_CONTRIBUTIONS TO_ THE THEORY OF NATURAL SELECTION. A Series of Essays. BY ALFRED RUSSEL WALLACE, AUTHOR OF "THE MALAY ARCHIPELAGO, " ETC. , ETC. _SECOND EDITION, WITH CORRECTIONS AND ADDITIONS. _ New York: MACMILLAN AND CO. 1871. [_The Right of Translation and Reproduction is reserved. _] LONDON: PRINTED BY HEAD, HOLE & CO. , FARRINGDON STREET, AND IVY LANE, E. C. PREFACE. The present volume consists of essays which I have contributed tovarious periodicals, or read before scientific societies during the lastfifteen years, with others now printed for the first time. The two firstof the series are printed without alteration, because, having gained methe reputation of being an independent originator of the theory of"natural selection, " they may be considered to have some historicalvalue. I have added to them one or two very short explanatory notes, andhave given headings to subjects, to make them uniform with the rest ofthe book. The other essays have been carefully corrected, oftenconsiderably enlarged, and in some cases almost rewritten, so as toexpress more fully and more clearly the views which I hold at thepresent time; and as most of them originally appeared in publicationswhich have a very limited circulation, I believe that the larger portionof this volume will be new to many of my friends and to most of myreaders. I now wish to say a few words on the reasons which have led me topublish this work. The second essay, especially when taken in connectionwith the first, contains an outline sketch of the theory of theorigin of species (by means of what was afterwards termed by Mr. Darwin--"natural selection, ") as conceived by me before I had the leastnotion of the scope and nature of Mr. Darwin's labours. They werepublished in a way not likely to attract the attention of any butworking naturalists, and I feel sure that many who have heard of them, have never had the opportunity of ascertaining how much or how littlethey really contain. It therefore happens, that, while some writers giveme more credit than I deserve, others may very naturally class me withDr. Wells and Mr. Patrick Matthew, who, as Mr. Darwin has shown in thehistorical sketch given in the 4th and 5th Editions of the "Origin ofSpecies, " certainly propounded the fundamental principle of "naturalselection" before himself, but who made no further use of thatprinciple, and failed to see its wide and immensely importantapplications. The present work will, I venture to think, prove, that I both saw at thetime the value and scope of the law which I had discovered, and havesince been able to apply it to some purpose in a few original lines ofinvestigation. But here my claims cease. I have felt all my life, and Istill feel, the most sincere satisfaction that Mr. Darwin had been atwork long before me, and that it was not left for me to attempt to write"The Origin of Species. " I have long since measured my own strength, andknow well that it would be quite unequal to that task. Far abler menthan myself may confess, that they have not that untiring patience inaccumulating, and that wonderful skill in using, large masses of factsof the most varied kind, --that wide and accurate physiologicalknowledge, --that acuteness in devising and skill in carrying outexperiments, --and that admirable style of composition, at once clear, persuasive and judicial, --qualities, which in their harmoniouscombination mark out Mr. Darwin as the man, perhaps of all men nowliving, best fitted for the great work he has undertaken andaccomplished. My own more limited powers have, it is true, enabled me now and then toseize on some conspicuous group of unappropriated facts, and to searchout some generalization which might bring them under the reign of knownlaw; but they are not suited to that more scientific and more laboriousprocess of elaborate induction, which in Mr. Darwin's hands has led tosuch brilliant results. Another reason which has led me to publish this volume at the presenttime is, that there are some important points on which I differ from Mr. Darwin, and I wish to put my opinions on record in an easily accessibleform, before the publication of his new work, (already announced, ) inwhich I believe most of these disputed questions will be fullydiscussed. I will now give the date and mode of publication of each of the essaysin this volume, as well as the amount of alteration they have undergone. I. --ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF NEW SPECIES. First published in the "Annals and Magazine of Natural History, "September, 1855. Reprinted without alteration of the text. II. --ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY FROM THEORIGINAL TYPE. First published in the "Journal of the Proceedings of the LinnæanSociety, " August, 1858. Reprinted without alteration of the text, exceptone or two grammatical emendations. III. --MIMICRY AND OTHER PROTECTIVE RESEMBLANCES AMONG ANIMALS. First published in the "Westminster Review, " July, 1867. Reprinted witha few corrections and some important additions, among which I mayespecially mention Mr. Jenner Weir's observations and experiments on thecolours of the caterpillars eaten or rejected by birds. IV. --THE MALAYAN PAPILIONIDÆ, OR SWALLOW-TAILED BUTTERFLIES, ASILLUSTRATIVE OF THE THEORY OF NATURAL SELECTION. First published in the "Transactions of the Linnæan Society, " Vol. XXV. (read March, 1864), under the title, "On the Phenomena of Variation andGeographical Distribution, as illustrated by the Papilionidæ of theMalayan Region. " The introductory part of this essay is now reprinted, omitting tables, references to plates, &c. , with some additions, and several corrections. Owing to the publication of Dr. Felder's "Voyage of the Novara"(Lepidoptera) in the interval between the reading of my paper and itspublication, several of my new species must have their names changed forthose given to them by Dr. Felder, and this will explain the want ofagreement in some cases between the names used in this volume and thoseof the original paper. V. --ON INSTINCT IN MAN AND ANIMALS. Not previously published. VI. --THE PHILOSOPHY OF BIRDS' NESTS. First published in the "Intellectual Observer, " July, 1867. Reprintedwith considerable emendations and additions. VII. --A THEORY OF BIRDS' NESTS; SHOWING THE RELATION OF CERTAINDIFFERENCES OF COLOUR IN BIRDS TO THEIR MODE OF NIDIFICATION. First published in the "Journal of Travel and Natural History" (No. 2), 1868. Now reprinted with considerable emendations and additions, bywhich I have endeavoured more clearly to express, and more fully toillustrate, my meaning in those parts which have been misunderstood bymy critics. VIII. --CREATION BY LAW. First published in the "Quarterly Journal of Science, " October, 1867. Now reprinted with a few alterations and additions. IX. --THE DEVELOPMENT OF HUMAN RACES UNDER THE LAW OF NATURAL SELECTION. First published in the "Anthropological Review, " May, 1864. Nowreprinted with a few important alterations and additions. I had intendedto have considerably extended this essay, but on attempting it I foundthat I should probably weaken the effect without adding much to theargument. I have therefore preferred to leave it as it was firstwritten, with the exception of a few ill-considered passages which neverfully expressed my meaning. As it now stands, I believe it contains theenunciation of an important truth. X. --THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN. This is the further development of a few sentences at the end of anarticle on "Geological Time and the Origin of Species, " which appearedin the "Quarterly Review, " for April, 1869. I have here ventured totouch on a class of problems which are usually considered to be beyondthe boundaries of science, but which, I believe, will one day be broughtwithin her domain. * * * * * For the convenience of those who are acquainted with any of my essays intheir original form, I subjoin references to the more importantadditions and alterations now made to them. _ADDITIONS AND CORRECTIONS TO THE ESSAYS AS ORIGINALLY PUBLISHED_. Essays I. And II. Are unaltered, but short notes are added at pp. 19, 24, 29, and 40. III. --_Mimicry, and other Protective Resemblances among Animals. _ PAGE 53 Additional illustration of protective colouring in the case of the wood-dove and the robin. 63 On moths resembling bird's dung and mortar. 86 Correction of some names of African Papilios and a reference to Mr. Trimen's observations. 89 Mr. Jenner Weir's observation on birds which refused to eat _Spilosoma menthrasti_. 102 An additional case of snake mimicry in _Oxyrhopus trigeminus_. 107 Mr. Salvin's case of mimicry among hawks. 113 Name, _Diadema anomala_, added. 117 to 122. Use of gay colours in caterpillars, with an account of Mr. Jenner Weir's and Mr. Butler's observations. IV. --_The Malayan Papilionidæ or Swallow-tailed Butterflies, asillustrative of the Theory of Natural Selection. _ 135 to 140. Additions to the discussion on the rank of the Papilionidæ, and on the principles which determine the comparative rank of groups in the animal kingdom. 164 Illustration of variability from Mr. Baker's revision of the British Roses. 173 Additional facts, on local variations of colour. 196 Additional genus of birds (Ceycopsis) peculiar to Celebes. 199, 200. Concluding remarks. VI. --_The Philosophy of Birds' Nests. _ 218 On nesting of Terns and Gulls, rewritten. 220 to 222. Daines Barrington, and others, on the song of birds. 223 On young birds learning to build, by memory and imitation. 224 Levaillant, on mode of nest-building. 229 On imperfect adaptation in birds' nests. VII. --_A Theory of Birds' Nests. _ 231, 232. Introductory passages modified, with some omissions. 233 How modifications of organization would affect the form of the nest. 235 Illustration from the habits of children and savages. 235, 236. Objection to term "hereditary habit" answered. 237 Passage rewritten, on more or less variable characters in relation to nidification. 248 On males choosing or rejecting females, and on the various modes in which colour may be acquired by female birds. 249 On probable ancestral colours of female birds. 255 Protective colouring of the Waxwing. VIII. --_Creation by Law. _ 293 Amount of variation in dogs. 296, 297. The "Times" on Natural Selection. 298 to 300. On intermediate or generalized forms of extinct animals as an indication of transmutation or development. 302 Tabular demonstration of the Origin of Species by Natural Selection. IX. --_The development of Human Races, under the law of NaturalSelection. _ 316 On colour as perhaps correlated with immunity from disease in man. 326, 327. On the probable future development of man. 330 Concluding paragraph rewritten. _London, March, 1870. _ PREFACE TO THE SECOND EDITION. The flattering reception of my Essays by the public and the press havingled to a second edition being called for within a year of its firstpublication, I have taken the opportunity to make a few necessarycorrections. I have also added a few passages to the 6th and 7th Essays, and have given two notes, explanatory of some portions of the lastchapter which appear to have been not always understood. These additionsare as follows:-- +-------------------------------------------------------------------+ | _To avoid altering the paging the additional pages now given have | | been lettered. _ | +---------+---------+-----------------------------------------------+ | 1st Ed. | 2nd Ed. | | +---------+---------+ | | 221 | 221 | Additional facts as to birds acquiring | | | | the song of other species. | | | | | | 223 | 223A } | Mr. Spruce's remarks on young birds | | | 223B } | pairing with old. | | | | | | 228 | 228A } | Pouchet's observations on a change | | | 228B } | in the nests of swallows. | | | | | | 229 | -- | Passage omitted about nest of Golden | | | | Crested Warbler, which had been | | | | inserted on Rennie's authority, but | | | | has not been confirmed by any later | | | | observers. | | | | | | 261 | 261 | Daines Barrington, on importance of | | | | protection to the female bird. | | | | | | | 372 | Note A. | | | | | | | 372B | Note B. | +---------+---------+-----------------------------------------------+ CONTENTS. I. --_On the Law which has regulated the introduction of New Species. _ Pp. 1-25 Geographical distribution dependent on Geologic Changes A Law deduced from well-known Geographical and Geological facts The form of a true system of Classification determined by this Law Geographical Distribution of Organisms Geological Distribution of the forms of Life High Organization of very ancient Animals consistent with this Law Objections to Forbes' Theory of Polarity Rudimentary Organs Conclusion II. --_On the Tendency of Varieties to depart indefinitely from the Original Type. _ Pp. 26-44 Instability of Varieties supposed to prove the permanent distinctness of Species The Struggle for Existence The Law of Population of Species The Abundance or Rarity of a Species dependent upon its more or less perfect Adaptation to the Conditions of Existence Useful Variations will tend to Increase, useless or hurtful Variations to Diminish Superior Varieties will ultimately extirpate the Original Species The Partial Reversion of Domesticated Varieties explained Lamarck's Hypothesis very different from that now advanced Conclusion III. --_Mimicry, and other Protective Resemblances among Animals. _ Pp. 45-129 Test of true and false Theories Importance of the Principle of Utility Popular Theories of Colour in Animals Importance of Concealment as influencing Colour Special modifications of Colour Theory of Protective Colouring Objection that Colour as being dangerous should not exist in Nature Mimicry Mimicry among Lepidoptera Lepidoptera mimicking other Insects Mimicry among Beetles Beetles mimicking other Insects Insects mimicking Species of other Orders Cases of Mimicry among the Vertebrata Mimicry among Snakes Mimicry among Birds Mimicry among Mammals Objections to Mr. Bates' Theory of Mimicry Mimicry by Female Insects only Cause of the dull Colours of Female Birds Use of the gaudy Colours of many Caterpillars Summary General deductions as to Colour in Nature Conclusion IV. --_The Malayan Papilionidæ, or Swallow-tailed Butterflies, as illustrative of the Theory of Natural Selection. _ Pp. 130-200 Special value of the Diurnal Lepidoptera for inquiries of this Nature Question of the rank of the Papilionidæ Distribution of the Papilionidæ Definition of the word Species Laws and Modes of Variation Simple Variability Polymorphism or Dimorphism Local form or variety Co-existing Variety Race or Subspecies Species Variation as specially influenced by Locality Local Variation of Size Local Variation of Form Local Variations of Colour Remarks on the facts of Local Variation Mimicry Concluding Remarks on Variation in Lepidoptera Arrangement and Geographical Distribution of the Malayan Papilionidæ Arrangement Geographical Distribution Range of the Groups of Malayan Papilionidæ Remarkable peculiarities of the island of Celebes Concluding Remarks V. --_On Instinct in Man and Animals. _ Pp. 201-210 How Instinct may be best Studied Definition of Instinct Does Man possess Instincts? How Indians travel through unknown and trackless Forests VI. --_The Philosophy of Birds' Nests. _ Pp. 211-230 Instinct or Reason in the Construction of Birds' Nests Do Men build by Reason or by Imitation? Why does each Bird build a peculiar kind of Nest? How do young Birds learn to build their first Nest? Do Birds sing by Instinct or by Imitation? Man's Works mainly Imitative How young Birds may learn to build Nests. Birds do Alter and Improve their Nests when altered conditions require it Conclusion VII. --_A Theory of Birds' Nests; showing the relation of certain differences of colour in female birds to their mode of nidification. _ Pp. 231-263 Changed Conditions and persistent Habits as influencing Nidification Classification of Nests Sexual differences of Colour in Birds The Law which connects the Colours of Female Birds with the mode of Nidification What the Facts Teach us Colour more variable than Structure or Habits, and therefore the Character which has generally been modified Exceptional cases confirmatory of the above Explanation Real or apparent exceptions to the Law stated at p. 240 Various modes of Protection of Animals Females of some groups require and obtain more Protection than the Males Conclusion VIII. --_Creation by Law. _ Pp. 264-301 Laws from which the Origin of Species may be deduced Mr. Darwin's Metaphors liable to Misconception A case of Orchis-structure explained by Natural Selection Adaptation brought about by General Laws Beauty in Nature How new Forms are produced by Variation and Selection The Objection that there are Limits to Variation Objection to the argument from Classification The _Times_ on Natural Selection Intermediate or generalized forms of Extinct Animals an indication of Transmutation or Development Conclusion A Demonstration of the Origin of Species IX. --_The Development of Human Races under the Law of Natural Selection_. Pp. 302-331 Wide difference of Opinion as to Man's Origin Outline of the Theory of Natural Selection Different effects of Natural Selection on Animals and on Man Influence of External Nature in the development of the Human Mind Extinction of Lower Races The Origin of the Races of Man The Bearing of these views on the Antiquity of Man Their Bearing on the Dignity and Supremacy of Man Their Bearing on the future Development of Man Summary Conclusion X. --_The Limits of Natural Selection as applied to Man. _ Pp. 333--371 What Natural Selection can Not do The Brain of the Savage shown to be Larger than he Needs it to be Size of Brain an important Element of Mental Power Comparison of the Brains of Man and of Anthropoid Apes Range of intellectual power in Man Intellect of Savages and of Animals compared The use of the Hairy Covering of Mammalia The Constant absence of Hair from certain parts of Man's body a remarkable Phenomenon Savage Man feels the want of this Hairy Covering Man's Naked Skin could not have been produced by Natural Selection Feet and Hands of Man considered as Difficulties on the Theory of Natural Selection The Origin of Some of Man's Mental Faculties, by the preservation of Useful Variations, not possible Difficulty as to the Origin of the Moral Sense Summary of the Argument as to the Insufficiency of Natural Selection to account for the Development of Man The Origin of Consciousness The Nature of Matter Matter is Force All Force is probably Will-force Conclusion I. ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF NEW SPECIES. [A] +--------------------------------------------------------------+ | [A] Written at Sarawak in February, 1855, and published in | | the "Annals and Magazine of Natural History, " September, | | 1855. | +--------------------------------------------------------------+ _Geographical Distribution dependent on Geologic Changes. _ Every naturalist who has directed his attention to the subject of thegeographical distribution of animals and plants, must have beeninterested in the singular facts which it presents. Many of these factsare quite different from what would have been anticipated, and havehitherto been considered as highly curious, but quite inexplicable. Noneof the explanations attempted from the time of Linnæus are nowconsidered at all satisfactory; none of them have given a causesufficient to account for the facts known at the time, or comprehensiveenough to include all the new facts which have since been, and are dailybeing added. Of late years, however, a great light has been thrown uponthe subject by geological investigations, which have shown that thepresent state of the earth and of the organisms now inhabiting it, isbut the last stage of a long and uninterrupted series of changes whichit has undergone, and consequently, that to endeavour to explain andaccount for its present condition without any reference to those changes(as has frequently been done) must lead to very imperfect and erroneousconclusions. The facts proved by geology are briefly these:--That during an immense, but unknown period, the surface of the earth has undergone successivechanges; land has sunk beneath the ocean, while fresh land has risen upfrom it; mountain chains have been elevated; islands have been formedinto continents, and continents submerged till they have become islands;and these changes have taken place, not once merely, but perhapshundreds, perhaps thousands of times:--That all these operations havebeen more or less continuous, but unequal in their progress, and duringthe whole series the organic life of the earth has undergone acorresponding alteration. This alteration also has been gradual, butcomplete; after a certain interval not a single species existing whichhad lived at the commencement of the period. This complete renewal ofthe forms of life also appears to have occurred several times:--Thatfrom the last of the geological epochs to the present or historicalepoch, the change of organic life has been gradual: the first appearanceof animals now existing can in many cases be traced, their numbersgradually increasing in the more recent formations, while other speciescontinually die out and disappear, so that the present condition of theorganic world is clearly derived by a natural process of gradualextinction and creation of species from that of the latest geologicalperiods. We may therefore safely infer a like gradation and naturalsequence from one geological epoch to another. Now, taking this as a fair statement of the results of geologicalinquiry, we see that the present geographical distribution of life uponthe earth must be the result of all the previous changes, both of thesurface of the earth itself and of its inhabitants. Many causes, nodoubt, have operated of which we must ever remain in ignorance, and wemay, therefore, expect to find many details very difficult ofexplanation, and in attempting to give one, must allow ourselves to callinto our service geological changes which it is highly probable may haveoccurred, though we have no direct evidence of their individualoperation. The great increase of our knowledge within the last twenty years, bothof the present and past history of the organic world, has accumulated abody of facts which should afford a sufficient foundation for acomprehensive law embracing and explaining them all, and giving adirection to new researches. It is about ten years since the idea ofsuch a law suggested itself to the writer of this essay, and he hassince taken every opportunity of testing it by all the newly-ascertainedfacts with which he has become acquainted, or has been able to observehimself. These have all served to convince him of the correctness of hishypothesis. Fully to enter into such a subject would occupy much space, and it is only in consequence of some views having been latelypromulgated, he believes, in a wrong direction, that he now ventures topresent his ideas to the public, with only such obvious illustrations ofthe arguments and results as occur to him in a place far removed fromall means of reference and exact information. _A Law deduced from well-known Geographical and Geological Facts. _ The following propositions in Organic Geography and Geology give themain facts on which the hypothesis is founded. Geography. 1. Large groups, such as classes and orders, are generally spread overthe whole earth, while smaller ones, such as families and genera, arefrequently confined to one portion, often to a very limited district. 2. In widely distributed families the genera are often limited in range;in widely distributed genera, well marked groups of species are peculiarto each geographical district. 3. When a group is confined to one district, and is rich in species, itis almost invariably the case that the most closely allied species arefound in the same locality or in closely adjoining localities, and thattherefore the natural sequence of the species by affinity is alsogeographical. 4. In countries of a similar climate, but separated by a wide sea orlofty mountains, the families, genera and species of the one are oftenrepresented by closely allied families, genera and species peculiar tothe other. Geology. 5. The distribution of the organic world in time is very similar to itspresent distribution in space. 6. Most of the larger and some small groups extend through severalgeological periods. 7. In each period, however, there are peculiar groups, found nowhereelse, and extending through one or several formations. 8. Species of one genus, or genera of one family occurring in the samegeological time are more closely allied than those separated in time. 9. As generally in geography no species or genus occurs in two verydistant localities without being also found in intermediate places, soin geology the life of a species or genus has not been interrupted. Inother words, no group or species has come into existence twice. 10. The following law may be deduced from these facts:--_Every specieshas come into existence coincident both in space and time with apre-existing closely allied species. _ This law agrees with, explains and illustrates all the facts connectedwith the following branches of the subject:--1st. The system of naturalaffinities. 2nd. The distribution of animals and plants in space. 3rd. The same in time, including all the phænomena of representative groups, and those which Professor Forbes supposed to manifest polarity. 4th. Thephænomena of rudimentary organs. We will briefly endeavour to show itsbearing upon each of these. _The Form of a true system of Classification determined by this Law. _ If the law above enunciated be true, it follows that the natural seriesof affinities will also represent the order in which the several speciescame into existence, each one having had for its immediate antitype aclosely allied species existing at the time of its origin. It isevidently possible that two or three distinct species may have had acommon antitype, and that each of these may again have become theantitypes from which other closely allied species were created. Theeffect of this would be, that so long as each species has had but onenew species formed on its model, the line of affinities will be simple, and may be represented by placing the several species in directsuccession in a straight line. But if two or more species have beenindependently formed on the plan of a common antitype, then the seriesof affinities will be compound, and can only be represented by a forkedor many branched line. Now, all attempts at a Natural classification andarrangement of organic beings show, that both these plans have obtainedin creation. Sometimes the series of affinities can be well representedfor a space by a direct progression from species to species or fromgroup to group, but it is generally found impossible so to continue. There constantly occur two or more modifications of an organ ormodifications of two distinct organs, leading us on to two distinctseries of species, which at length differ so much from each other as toform distinct genera or families. These are the parallel series orrepresentative groups of naturalists, and they often occur in differentcountries, or are found fossil in different formations. They are said tohave an analogy to each other when they are so far removed from theircommon antitype as to differ in many important points of structure, while they still preserve a family resemblance. We thus see howdifficult it is to determine in every case whether a given relation isan analogy or an affinity, for it is evident that as we go back alongthe parallel or divergent series, towards the common antitype, theanalogy which existed between the two groups becomes an affinity. We arealso made aware of the difficulty of arriving at a true classification, even in a small and perfect group;--in the actual state of nature it isalmost impossible, the species being so numerous and the modificationsof form and structure so varied, arising probably from the immensenumber of species which have served as antitypes for the existingspecies, and thus produced a complicated branching of the lines ofaffinity, as intricate as the twigs of a gnarled oak or the vascularsystem of the human body. Again, if we consider that we have onlyfragments of this vast system, the stem and main branches beingrepresented by extinct species of which we have no knowledge, while avast mass of limbs and boughs and minute twigs and scattered leaves iswhat we have to place in order, and determine the true position eachoriginally occupied with regard to the others, the whole difficulty ofthe true Natural System of classification becomes apparent to us. We shall thus find ourselves obliged to reject all these systems ofclassification which arrange species or groups in circles, as well asthese which fix a definite number for the divisions of each group. Thelatter class have been very generally rejected by naturalists, ascontrary to nature, notwithstanding the ability with which they havebeen advocated; but the circular system of affinities seems to haveobtained a deeper hold, many eminent naturalists having to some extentadopted it. We have, however, never been able to find a case in whichthe circle has been closed by a direct and close affinity. In most casesa palpable analogy has been substituted, in others the affinity is veryobscure or altogether doubtful. The complicated branching of the linesof affinities in extensive groups must also afford great facilities forgiving a show of probability to any such purely artificial arrangements. Their death-blow was given by the admirable paper of the lamented Mr. Strickland, published in the "Annals of Natural History, " in which he soclearly showed the true synthetical method of discovering the NaturalSystem. _Geographical Distribution of Organisms. _ If we now consider the geographical distribution of animals and plantsupon the earth, we shall find all the facts beautifully in accordancewith, and readily explained by, the present hypothesis. A country havingspecies, genera, and whole families peculiar to it, will be thenecessary result of its having been isolated for a long period, sufficient for many series of species to have been created on the typeof pre-existing ones, which, as well as many of the earlier-formedspecies, have become extinct, and thus made the groups appear isolated. If in any case the antitype had an extensive range, two or more groupsof species might have been formed, each varying from it in a differentmanner, and thus producing several representative or analogous groups. The Sylviadæ of Europe and the Sylvicolidæ of North America, theHeliconidæ of South America and the Euploeas of the East, the group ofTrogons inhabiting Asia, and that peculiar to South America, areexamples that may be accounted for in this manner. Such phænomena as are exhibited by the Galapagos Islands, which containlittle groups of plants and animals peculiar to themselves, but mostnearly allied to those of South America, have not hitherto received any, even a conjectural explanation. The Galapagos are a volcanic group ofhigh antiquity, and have probably never been more closely connected withthe continent than they are at present. They must have been firstpeopled, like other newly-formed islands, by the action of winds andcurrents, and at a period sufficiently remote to have had the originalspecies die out, and the modified prototypes only remain. In the sameway we can account for the separate islands having each their peculiarspecies, either on the supposition that the same original emigrationpeopled the whole of the islands with the same species from whichdifferently modified prototypes were created, or that the islands weresuccessively peopled from each other, but that new species have beencreated in each on the plan of the pre-existing ones. St. Helena is asimilar case of a very ancient island having obtained an entirelypeculiar, though limited, flora. On the other hand, no example is knownof an island which can be proved geologically to be of very recentorigin (late in the Tertiary, for instance), and yet possesses genericor family groups, or even many species peculiar to itself. When a range of mountains has attained a great elevation, and has soremained during a long geological period, the species of the two sidesat and near their bases will be often very different, representativespecies of some genera occurring, and even whole genera being peculiarto one side only, as is remarkably seen in the case of the Andes andRocky Mountains. A similar phænomenon occurs when an island has beenseparated from a continent at a very early period. The shallow seabetween the Peninsula of Malacca, Java, Sumatra and Borneo was probablya continent or large island at an early epoch, and may have becomesubmerged as the volcanic ranges of Java and Sumatra were elevated. Theorganic results we see in the very considerable number of species ofanimals common to some or all of these countries, while at the same timea number of closely allied representative species exist peculiar toeach, showing that a considerable period has elapsed since theirseparation. The facts of geographical distribution and of geology maythus mutually explain each other in doubtful cases, should theprinciples here advocated be clearly established. In all those cases in which an island has been separated from acontinent, or raised by volcanic or coralline action from the sea, or inwhich a mountain-chain has been elevated in a recent geological epoch, the phænomena of peculiar groups or even of single representativespecies will not exist. Our own island is an example of this, itsseparation from the continent being geologically very recent, and wehave consequently scarcely a species which is peculiar to it; while theAlpine range, one of the most recent mountain elevations, separatesfaunas and floras which scarcely differ more than may be due to climateand latitude alone. The series of facts alluded to in Proposition (3), of closely alliedspecies in rich groups being found geographically near each other, ismost striking and important. Mr. Lovell Reeve has well exemplified it inhis able and interesting paper on the Distribution of the Bulimi. It isalso seen in the Humming-birds and Toucans, little groups of two orthree closely allied species being often found in the same or closelyadjoining districts, as we have had the good fortune of personallyverifying. Fishes give evidence of a similar kind: each great river hasits peculiar genera, and in more extensive genera its groups of closelyallied species. But it is the same throughout Nature; every class andorder of animals will contribute similar facts. Hitherto no attempt hasbeen made to explain these singular phenomena, or to show how they havearisen. Why are the genera of Palms and of Orchids in almost every caseconfined to one hemisphere? Why are the closely allied species ofbrown-backed Trogons all found in the East, and the green-backed in theWest? Why are the Macaws and the Cockatoos similarly restricted? Insectsfurnish a countless number of analogous examples;--the Goliathi ofAfrica, the Ornithopteræ of the Indian Islands, the Heliconidæ of SouthAmerica, the Danaidæ of the East, and in all, the most closely alliedspecies found in geographical proximity. The question forces itselfupon every thinking mind, --why are these things so? They could not be asthey are had no law regulated their creation and dispersion. The lawhere enunciated not merely explains, but necessitates the facts we seeto exist, while the vast and long-continued geological changes of theearth readily account for the exceptions and apparent discrepancies thathere and there occur. The writer's object in putting forward his viewsin the present imperfect manner is to submit them to the test of otherminds, and to be made aware of all the facts supposed to be inconsistentwith them. As his hypothesis is one which claims acceptance solely asexplaining and connecting facts which exist in nature, he expects factsalone to be brought to disprove it, not _à priori_ arguments against itsprobability. _Geological Distribution of the Forms of Life. _ The phænomena of geological distribution are exactly analogous to thoseof geography. Closely allied species are found associated in the samebeds, and the change from species to species appears to have been asgradual in time as in space. Geology, however, furnishes us withpositive proof of the extinction and production of species, though itdoes not inform us how either has taken place. The extinction ofspecies, however, offers but little difficulty, and the _modus operandi_has been well illustrated by Sir C. Lyell in his admirable"Principles. " Geological changes, however gradual, must occasionallyhave modified external conditions to such an extent as to have renderedthe existence of certain species impossible. The extinction would inmost cases be effected by a gradual dying-out, but in some instancesthere might have been a sudden destruction of a species of limitedrange. To discover how the extinct species have from time to time beenreplaced by new ones down to the very latest geological period, is themost difficult, and at the same time the most interesting problem in thenatural history of the earth. The present inquiry, which seeks toeliminate from known facts a law which has determined, to a certaindegree, what species could and did appear at a given epoch, may, it ishoped, be considered as one step in the right direction towards acomplete solution of it. _High Organization of very ancient Animals consistent with this Law. _ Much discussion has of late years taken place on the question, whetherthe succession of life upon the globe has been from a lower to a higherdegree of organization. The admitted facts seem to show that there hasbeen a general, but not a detailed progression. Mollusca and Radiataexisted before Vertebrata, and the progression from Fishes to Reptilesand Mammalia, and also from the lower mammals to the higher, isindisputable. On the other hand, it is said that the Mollusca andRadiata of the very earliest periods were more highly organized than thegreat mass of those now existing, and that the very first fishes thathave been discovered are by no means the lowest organised of the class. Now it is believed the present hypothesis will harmonize with all thesefacts, and in a great measure serve to explain them; for though it mayappear to some readers essentially a theory of progression, it is inreality only one of gradual change. It is, however, by no meansdifficult to show that a real progression in the scale of organizationis perfectly consistent with all the appearances, and even with apparentretrogression, should such occur. Returning to the analogy of a branching tree, as the best mode ofrepresenting the natural arrangement of species and their successivecreation, let us suppose that at an early geological epoch any group(say a class of the Mollusca) has attained to a great richness ofspecies and a high organization. Now let this great branch of alliedspecies, by geological mutations, be completely or partially destroyed. Subsequently a new branch springs from the same trunk, that is to say, new species are successively created, having for their antitypes thesame lower organized species which had served as the antitypes for theformer group, but which have survived the modified conditions whichdestroyed it. This new group being subject to these altered conditions, has modifications of structure and organization given to it, andbecomes the representative group of the former one in another geologicalformation. It may, however, happen, that though later in time, the newseries of species may never attain to so high a degree of organizationas those preceding it, but in its turn become extinct, and give place toyet another modification from the same root, which may be of higher orlower organization, more or less numerous in species, and more or lessvaried in form and structure than either of those which preceded it. Again, each of these groups may not have become totally extinct, but mayhave left a few species, the modified prototypes of which have existedin each succeeding period, a faint memorial of their former grandeur andluxuriance. Thus every case of apparent retrogression may be in realitya progress, though an interrupted one: when some monarch of the forestloses a limb, it may be replaced by a feeble and sickly substitute. Theforegoing remarks appear to apply to the case of the Mollusca, which, ata very early period, had reached a high organization and a greatdevelopment of forms and species in the testaceous Cephalopoda. In eachsucceeding age modified species and genera replaced the former oneswhich had become extinct, and as we approach the present æra, but fewand small representatives of the group remain, while the Gasteropods andBivalves have acquired an immense preponderance. In the long series ofchanges the earth has undergone, the process of peopling it with organicbeings has been continually going on, and whenever any of the highergroups have become nearly or quite extinct, the lower forms which havebetter resisted the modified physical conditions have served as theantitypes on which to found the new races. In this manner alone, it isbelieved, can the representative groups at successive periods, and therisings and fallings in the scale of organization, be in every caseexplained. _Objections to Forbes' Theory of Polarity. _ The hypothesis of polarity, recently put forward by Professor EdwardForbes to account for the abundance of generic forms at a very earlyperiod and at present, while in the intermediate epochs there is agradual diminution and impoverishment, till the minimum occurred at theconfines of the Palæozoic and Secondary epochs, appears to us quiteunnecessary, as the facts may be readily accounted for on the principlesalready laid down. Between the Palæozoic and Neozoic periods ofProfessor Forbes, there is scarcely a species in common, and the greaterpart of the genera and families also disappear to be replaced by newones. It is almost universally admitted that such a change in theorganic world must have occupied a vast period of time. Of this intervalwe have no record; probably because the whole area of the earlyformations now exposed to our researches was elevated at the end of thePalæozoic period, and remained so through the interval required for theorganic changes which resulted in the fauna and flora of the Secondaryperiod. The records of this interval are buried beneath the ocean whichcovers three-fourths of the globe. Now it appears highly probable that along period of quiescence or stability in the physical conditions of adistrict would be most favourable to the existence of organic life inthe greatest abundance, both as regards individuals and also as tovariety of species and generic group, just as we now find that theplaces best adapted to the rapid growth and increase of individuals alsocontain the greatest profusion of species and the greatest variety offorms, --the tropics in comparison with the temperate and arctic regions. On the other hand, it seems no less probable that a change in thephysical conditions of a district, even small in amount if rapid, oreven gradual if to a great amount, would be highly unfavourable to theexistence of individuals, might cause the extinction of many species, and would probably be equally unfavourable to the creation of new ones. In this too we may find an analogy with the present state of our earth, for it has been shown to be the violent extremes and rapid changes ofphysical conditions, rather than the actual mean state in the temperateand frigid zones, which renders them less prolific than the tropicalregions, as exemplified by the great distance beyond the tropics towhich tropical forms penetrate when the climate is equable, and also bythe richness in species and forms of tropical mountain regions whichprincipally differ from the temperate zone in the uniformity of theirclimate. However this may be, it seems a fair assumption that during aperiod of geological repose the new species which we know to have beencreated would have appeared; that the creations would then exceed innumber the extinctions, and therefore the number of species wouldincrease. In a period of geological activity, on the other hand, itseems probable that the extinctions might exceed the creations, and thenumber of species consequently diminish. That such effects did takeplace in connexion with the causes to which we have imputed them, isshown in the case of the Coal formation, the faults and contortions ofwhich show a period of great activity and violent convulsions, and it isin the formation immediately succeeding this that the poverty of formsof life is most apparent. We have then only to suppose a long period ofsomewhat similar action during the vast unknown interval at thetermination of the Palæozoic period, and then a decreasing violence orrapidity through the Secondary period, to allow for the gradualrepopulation of the earth with varied forms, and the whole of the factsare explained. [B] We thus have a clue to the increase of the forms oflife during certain periods, and their decrease during others, withoutrecourse to any causes but those we know to have existed, and toeffects fairly deducible from them. The precise manner in which thegeological changes of the early formations were effected is so extremelyobscure, that when we can explain important facts by a retardation atone time and an acceleration at another of a process which we know fromits nature and from observation to have been unequal, --a cause so simplemay surely be preferred to one so obscure and hypothetical as polarity. +--------------------------------------------------------------+ | [B] Professor Ramsay has since shown that a glacial epoch | | probably occurred at the time of the Permian formation, | | which will more satisfactorily account for the comparative | | poverty of species. | +--------------------------------------------------------------+ I would also venture to suggest some reasons against the very nature ofthe theory of Professor Forbes. Our knowledge of the organic worldduring any geological epoch is necessarily very imperfect. Looking atthe vast numbers of species and groups that have been discovered bygeologists, this may be doubted; but we should compare their numbers notmerely with those that now exist upon the earth, but with a far largeramount. We have no reason for believing that the number of species onthe earth at any former period was much less than at present; at allevents the aquatic portion, with which geologists have mostacquaintance, was probably often as great or greater. Now we know thatthere have been many complete changes of species; new sets of organismshave many times been introduced in place of old ones which have becomeextinct, so that the total amount which have existed on the earth fromthe earliest geological period must have borne about the same proportionto those now living, as the whole human race who have lived and diedupon the earth, to the population at the present time. Again, at eachepoch, the whole earth was no doubt, as now, more or less the theatre oflife, and as the successive generations of each species died, theirexuviæ and preservable parts would be deposited over every portion ofthe then existing seas and oceans, which we have reason for supposing tohave been more, rather than less, extensive than at present. In orderthen to understand our possible knowledge of the early world and itsinhabitants, we must compare, not the area of the whole field of ourgeological researches with the earth's surface, but the area of theexamined portion of each formation separately with the whole earth. Forexample, during the Silurian period all the earth was Silurian, andanimals were living and dying, and depositing their remains more or lessover the whole area of the globe, and they were probably (the species atleast) nearly as varied in different latitudes and longitudes as atpresent. What proportion do the Silurian districts bear to the wholesurface of the globe, land and sea (for far more extensive Siluriandistricts probably exist beneath the ocean than above it), and whatportion of the known Silurian districts has been actually examined forfossils? Would the area of rock actually laid open to the eye be thethousandth or the ten-thousandth part of the earth's surface? Ask thesame question with regard to the Oolite or the Chalk, or even toparticular beds of these when they differ considerably in theirfossils, and you may then get some notion of how small a portion of thewhole we know. But yet more important is the probability, nay almost the certainty, that whole formations containing the records of vast geological periodsare entirely buried beneath the ocean, and for ever beyond our reach. Most of the gaps in the geological series may thus be filled up, andvast numbers of unknown and unimaginable animals, which might help toelucidate the affinities of the numerous isolated groups which are aperpetual puzzle to the zoologist, may there be buried, till futurerevolutions may raise them in their turn above the waters, to affordmaterials for the study of whatever race of intelligent beings may thenhave succeeded us. These considerations must lead us to the conclusion, that our knowledge of the whole series of the former inhabitants of theearth is necessarily most imperfect and fragmentary, --as much so as ourknowledge of the present organic world would be, were we forced to makeour collections and observations only in spots equally limited in areaand in number with those actually laid open for the collection offossils. Now, the hypothesis of Professor Forbes is essentially one thatassumes to a great extent the completeness of our knowledge of the wholeseries of organic beings which have existed on the earth. Thisappears to be a fatal objection to it, independently of all otherconsiderations. It may be said that the same objections exist againstevery theory on such a subject, but this is not necessarily the case. The hypothesis put forward in this paper depends in no degree upon thecompleteness of our knowledge of the former condition of the organicworld, but takes what facts we have as fragments of a vast whole, anddeduces from them something of the nature and proportions of that wholewhich we can never know in detail. It is founded upon isolated groups offacts, recognizes their isolation, and endeavours to deduce from themthe nature of the intervening portions. _Rudimentary Organs. _ Another important series of facts, quite in accordance with, and evennecessary deductions from, the law now developed, are those ofrudimentary organs. That these really do exist, and in most cases haveno special function in the animal oeconomy, is admitted by the firstauthorities in comparative anatomy. The minute limbs hidden beneath theskin in many of the snake-like lizards, the anal hooks of the boaconstrictor, the complete series of jointed finger-bones in the paddleof the Manatus and whale, are a few of the most familiar instances. Inbotany a similar class of facts has been long recognised. Abortivestamens, rudimentary floral envelopes and undeveloped carpels, are ofthe most frequent occurrence. To every thoughtful naturalist thequestion must arise, What are these for? What have they to do with thegreat laws of creation? Do they not teach us something of the system ofNature? If each species has been created independently, and without anynecessary relations with pre-existing species, what do these rudiments, these apparent imperfections mean? There must be a cause for them; theymust be the necessary results of some great natural law. Now, if, as ithas been endeavoured to be shown, the great law which has regulated thepeopling of the earth with animal and vegetable life is, that everychange shall be gradual; that no new creature shall be formed widelydiffering from anything before existing; that in this, as in everythingelse in Nature, there shall be gradation and harmony, --then theserudimentary organs are necessary, and are an essential part of thesystem of Nature. Ere the higher Vertebrata were formed, for instance, many steps were required, and many organs had to undergo modificationsfrom the rudimental condition in which only they had as yet existed. Westill see remaining an antitypal sketch of a wing adapted for flight inthe scaly flapper of the penguin, and limbs first concealed beneath theskin, and then weakly protruding from it, were the necessary gradationsbefore others should be formed fully adapted for locomotion. [C] Manymore of these modifications should we behold, and more complete seriesof them, had we a view of all the forms which have ceased to live. Thegreat gaps that exist between fishes, reptiles, birds, and mammals wouldthen, no doubt, be softened down by intermediate groups, and the wholeorganic world would be seen to be an unbroken and harmonious system. +--------------------------------------------------------------+ | [C] The theory of Natural Selection has now taught us that | | these are not the steps by which limbs have been formed; and | | that most rudimentary organs have been produced by abortion, | | owing to disuse, as explained by Mr. Darwin. | +--------------------------------------------------------------+ _Conclusion. _ It has now been shown, though most briefly and imperfectly, how the lawthat "_Every species has come into existence coincident both in time andspace with a pre-existing closely allied species_, " connects togetherand renders intelligible a vast number of independent and hithertounexplained facts. The natural system of arrangement of organic beings, their geographical distribution, their geological sequence, thephænomena of representative and substituted groups in all theirmodifications, and the most singular peculiarities of anatomicalstructure, are all explained and illustrated by it, in perfectaccordance with the vast mass of facts which the researches of modernnaturalists have brought together, and, it is believed, not materiallyopposed to any of them. It also claims a superiority over previoushypotheses, on the ground that it not merely explains, but necessitateswhat exists. Granted the law, and many of the most important facts inNature could not have been otherwise, but are almost as necessarydeductions from it, as are the elliptic orbits of the planets from thelaw of gravitation. II. ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY FROM THE ORIGINALTYPE. [D] +--------------------------------------------------------------+ | [D] Written at Ternate, February, 1858; and published in the | | Journal of the Proceedings of the Linnæan Society for | | August, 1858. | +--------------------------------------------------------------+ _Instability of Varieties supposed to prove the permanent distinctnessof Species. _ One of the strongest arguments which have been adduced to prove theoriginal and permanent distinctness of species is, that _varieties_produced in a state of domesticity are more or less unstable, and oftenhave a tendency, if left to themselves, to return to the normal form ofthe parent species; and this instability is considered to be adistinctive peculiarity of all varieties, even of those occurring amongwild animals in a state of nature, and to constitute a provision forpreserving unchanged the originally created distinct species. In the absence or scarcity of facts and observations as to _varieties_occurring among wild animals, this argument has had great weight withnaturalists, and has led to a very general and somewhat prejudicedbelief in the stability of species. Equally general, however, is thebelief in what are called "permanent or true varieties, "--races ofanimals which continually propagate their like, but which differ soslightly (although constantly) from some other race, that the one isconsidered to be a _variety_ of the other. Which is the _variety_ andwhich the original _species_, there is generally no means ofdetermining, except in those rare cases in which the one race has beenknown to produce an offspring unlike itself and resembling the other. This, however, would seem quite incompatible with the "permanentinvariability of species, " but the difficulty is overcome by assumingthat such varieties have strict limits, and can never again vary furtherfrom the original type, although they may return to it, which, from theanalogy of the domesticated animals, is considered to be highlyprobable, if not certainly proved. It will be observed that this argument rests entirely on the assumption, that _varieties_ occurring in a state of nature are in all respectsanalogous to or even identical with those of domestic animals, and aregoverned by the same laws as regards their permanence or furthervariation. But it is the object of the present paper to show that thisassumption is altogether false, that there is a general principle innature which will cause many _varieties_ to survive the parent species, and to give rise to successive variations departing further and furtherfrom the original type; and which also produces, in domesticatedanimals, the tendency of varieties to return to the parent form. _The Struggle for Existence. _ The life of wild animals is a struggle for existence. The full exertionof all their faculties and all their energies is required to preservetheir own existence and provide for that of their infant offspring. Thepossibility of procuring food during the least favourable seasons, andof escaping the attacks of their most dangerous enemies, are the primaryconditions which determine the existence both of individuals and ofentire species. These conditions will also determine the population of aspecies; and by a careful consideration of all the circumstances we maybe enabled to comprehend, and in some degree to explain, what at firstsight appears so inexplicable--the excessive abundance of some species, while others closely allied to them are very rare. _The Law of Population of Species. _ The general proportion that must obtain between certain groups ofanimals is readily seen. Large animals cannot be so abundant as smallones; the carnivora must be less numerous than the herbivora; eagles andlions can never be so plentiful as pigeons and antelopes; and the wildasses of the Tartarian deserts cannot equal in numbers the horses of themore luxuriant prairies and pampas of America. The greater or lessfecundity of an animal is often considered to be one of the chief causesof its abundance or scarcity; but a consideration of the facts will showus that it really has little or nothing to do with the matter. Even theleast prolific of animals would increase rapidly if unchecked, whereasit is evident that the animal population of the globe must bestationary, or perhaps, through the influence of man, decreasing. Fluctuations there may be; but permanent increase, except in restrictedlocalities, is almost impossible. For example, our own observation mustconvince us that birds do not go on increasing every year in ageometrical ratio, as they would do, were there not some powerful checkto their natural increase. Very few birds produce less than two youngones each year, while many have six, eight, or ten; four will certainlybe below the average; and if we suppose that each pair produce youngonly four times in their life, that will also be below the average, supposing them not to die either by violence or want of food. Yet atthis rate how tremendous would be the increase in a few years from asingle pair! A simple calculation will show that in fifteen years eachpair of birds would have increased to nearly ten millions![E] whereas wehave no reason to believe that the number of the birds of any countryincreases at all in fifteen or in one hundred and fifty years. With suchpowers of increase the population must have reached its limits, andhave become stationary, in a very few years after the origin of eachspecies. It is evident, therefore, that each year an immense number ofbirds must perish--as many in fact as are born; and as on the lowestcalculation the progeny are each year twice as numerous as theirparents, it follows that, whatever be the average number of individualsexisting in any given country, _twice that number must perishannually_, --a striking result, but one which seems at least highlyprobable, and is perhaps under rather than over the truth. It wouldtherefore appear that, as far as the continuance of the species and thekeeping up the average number of individuals are concerned, large broodsare superfluous. On the average all above _one_ become food for hawksand kites, wild cats or weasels, or perish of cold and hunger as wintercomes on. This is strikingly proved by the case of particular species;for we find that their abundance in individuals bears no relationwhatever to their fertility in producing offspring. +--------------------------------------------------------------+ | [E] This is under estimated. The number would really amount | | to more than two thousand millions! | +--------------------------------------------------------------+ Perhaps the most remarkable instance of an immense bird population isthat of the passenger pigeon of the United States, which lays only one, or at most two eggs, and is said to rear generally but one young one. Why is this bird so extraordinarily abundant, while others producing twoor three times as many young are much less plentiful? The explanation isnot difficult. The food most congenial to this species, and on which itthrives best, is abundantly distributed over a very extensive region, offering such differences of soil and climate, that in one part oranother of the area the supply never fails. The bird is capable of avery rapid and long-continued flight, so that it can pass withoutfatigue over the whole of the district it inhabits, and as soon as thesupply of food begins to fail in one place is able to discover a freshfeeding-ground. This example strikingly shows us that the procuring aconstant supply of wholesome food is almost the sole condition requisitefor ensuring the rapid increase of a given species, since neither thelimited fecundity, nor the unrestrained attacks of birds of prey and ofman are here sufficient to check it. In no other birds are thesepeculiar circumstances so strikingly combined. Either their food is moreliable to failure, or they have not sufficient power of wing to searchfor it over an extensive area, or during some season of the year itbecomes very scarce, and less wholesome substitutes have to be found;and thus, though more fertile in offspring, they can never increasebeyond the supply of food in the least favourable seasons. Many birds can only exist by migrating, when their food becomes scarce, to regions possessing a milder, or at least a different climate, though, as these migrating birds are seldom excessively abundant, it is evidentthat the countries they visit are still deficient in a constant andabundant supply of wholesome food. Those whose organization does notpermit them to migrate when their food becomes periodically scarce, cannever attain a large population. This is probably the reasons whywoodpeckers are scarce with us, while in the tropics they are among themost abundant of solitary birds. Thus the house sparrow is moreabundant than the redbreast, because its food is more constant andplentiful, --seeds of grasses being preserved during the winter, and ourfarm-yards and stubble-fields furnishing an almost inexhaustible supply. Why, as a general rule, are aquatic, and especially sea birds, verynumerous in individuals? Not because they are more prolific than others, generally the contrary; but because their food never fails, thesea-shores and river-banks daily swarming with a fresh supply of smallmollusca and crustacea. Exactly the same laws will apply to mammals. Wild cats are prolific and have few enemies; why then are they never asabundant as rabbits? The only intelligible answer is, that their supplyof food is more precarious. It appears evident, therefore, that so longas a country remains physically unchanged, the numbers of its animalpopulation cannot materially increase. If one species does so, someothers requiring the same kind of food must diminish in proportion. Thenumbers that die annually must be immense; and as the individualexistence of each animal depends upon itself, those that die must bethe weakest--the very young, the aged, and the diseased--while thosethat prolong their existence can only be the most perfect in health andvigour--those who are best able to obtain food regularly, and avoidtheir numerous enemies. It is, as we commenced by remarking, "a strugglefor existence, " in which the weakest and least perfectly organized mustalways succumb. _The Abundance or Rarity of a Species dependent upon its more or lessperfect Adaptation to the Conditions of Existence. _ It seems evident that what takes place among the individuals of aspecies must also occur among the several allied species of agroup, --viz. , that those which are best adapted to obtain a regularsupply of food, and to defend themselves against the attacks of theirenemies and the vicissitudes of the seasons, must necessarily obtain andpreserve a superiority in population; while those species which fromsome defect of power or organization are the least capable ofcounteracting the vicissitudes of food-supply, &c. , must diminish innumbers, and, in extreme cases, become altogether extinct. Between theseextremes the species will present various degrees of capacity forensuring the means of preserving life; and it is thus we account for theabundance or rarity of species. Our ignorance will generally prevent usfrom accurately tracing the effects to their causes; but could we becomeperfectly acquainted with the organization and habits of the variousspecies of animals, and could we measure the capacity of each forperforming the different acts necessary to its safety and existenceunder all the varying circumstances by which it is surrounded, we mightbe able even to calculate the proportionate abundance of individualswhich is the necessary result. If now we have succeeded in establishing these two points--1st, _thatthe animal population of a country is generally stationary, being keptdown by a periodical deficiency of food, and other checks_; and, 2nd, _that the comparative abundance or scarcity of the individuals of theseveral species is entirely due to their organization and resultinghabits, which, rendering it more difficult to procure a regular supplyof food and to provide for their personal safety in some cases than inothers, can only be balanced by a difference in the population whichhave to exist in a given area_--we shall be in a condition to proceed tothe consideration of _varieties_, to which the preceding remarks have adirect and very important application. _Useful Variations will tend to Increase; useless or hurtful Variationsto Diminish. _ Most or perhaps all the variations from the typical form of a speciesmust have some definite effect, however slight, on the habits orcapacities of the individuals. Even a change of colour might, byrendering them more or less distinguishable, affect their safety; agreater or less development of hair might modify their habits. Moreimportant changes, such as an increase in the power or dimensions of thelimbs or any of the external organs, would more or less affect theirmode of procuring food or the range of country which they could inhabit. It is also evident that most changes would affect, either favourably oradversely, the powers of prolonging existence. An antelope with shorteror weaker legs must necessarily suffer more from the attacks of thefeline carnivora; the passenger pigeon with less powerful wings wouldsooner or later be affected in its powers of procuring a regular supplyof food; and in both cases the result must necessarily be a diminutionof the population of the modified species. If, on the other hand, anyspecies should produce a variety having slightly increased powers ofpreserving existence, that variety must inevitably in time acquire asuperiority in numbers. These results must follow as surely as old age, intemperance, or scarcity of food produce an increased mortality. Inboth cases there may be many individual exceptions; but on the averagethe rule will invariably be found to hold good. All varieties willtherefore fall into two classes--those which under the same conditionswould never reach the population of the parent species, and those whichwould in time obtain and keep a numerical superiority. Now, let somealteration of physical conditions occur in the district--a long periodof drought, a destruction of vegetation by locusts, the irruption ofsome new carnivorous animal seeking "pastures new"--any change in facttending to render existence more difficult to the species in question, and tasking its utmost powers to avoid complete extermination; it isevident that, of all the individuals composing the species, thoseforming the least numerous and most feebly organized variety wouldsuffer first, and, were the pressure severe, must soon become extinct. The same causes continuing in action, the parent species would nextsuffer, would gradually diminish in numbers, and with a recurrence ofsimilar unfavourable conditions might also become extinct. Tho superiorvariety would then alone remain, and on a return to favourablecircumstances would rapidly increase in numbers and occupy the place ofthe extinct species and variety. _Superior Varieties will ultimately Extirpate the original Species. _ The _variety_ would now have replaced the _species_, of which it wouldbe a more perfectly developed and more highly organized form. It wouldbe in all respects better adapted to secure its safety, and to prolongits individual existence and that of the race. Such a variety _couldnot_ return to the original form; for that form is an inferior one, andcould never compete with it for existence. Granted, therefore, a"tendency" to reproduce the original type of the species, still thevariety must ever remain preponderant in numbers, and under adversephysical conditions _again alone survive_. But this new, improved, andpopulous race might itself, in course of time, give rise to newvarieties, exhibiting several diverging modifications of form, any ofwhich, tending to increase the facilities for preserving existence, must, by the same general law, in their turn become predominant. Here, then, we have _progression and continued divergence_ deduced from thegeneral laws which regulate the existence of animals in a state ofnature, and from the undisputed fact that varieties do frequently occur. It is not, however, contended that this result would be invariable; achange of physical conditions in the district might at times materiallymodify it, rendering the race which had been the most capable ofsupporting existence under the former conditions now the least so, andeven causing the extinction of the newer and, for a time, superior race, while the old or parent species and its first inferior varietiescontinued to flourish. Variations in unimportant parts might also occur, having no perceptible effect on the life-preserving powers; and thevarieties so furnished might run a course parallel with the parentspecies, either giving rise to further variations or returning to theformer type. All we argue for is, that certain varieties have a tendencyto maintain their existence longer than the original species, and thistendency must make itself felt; for though the doctrine of chances oraverages can never be trusted to on a limited scale, yet, if applied tohigh numbers, the results come nearer to what theory demands, and, as weapproach to an infinity of examples, become strictly accurate. Now thescale on which nature works is so vast--the numbers of individuals andthe periods of time with which she deals approach so near to infinity, than any cause, however slight, and however liable to be veiled andcounteracted by accidental circumstances, must in the end produce itsfull legitimate results. _The Partial Reversion of Domesticated Varieties explained. _ Let us now turn to domesticated animals, and inquire how varietiesproduced among them are affected by the principles here enunciated. Theessential difference in the condition of wild and domestic animals isthis, --that among the former, their well-being and very existence dependupon the full exercise and healthy condition of all their senses andphysical powers, whereas, among the latter, these are only partiallyexercised, and in some cases are absolutely unused. A wild animal has tosearch, and often to labour, for every mouthful of food--to exercisesight, hearing, and smell in seeking it, and in avoiding dangers, inprocuring shelter from the inclemency of the seasons, and in providingfor the subsistence and safety of its offspring. There is no muscle ofits body that is not called into daily and hourly activity; there is nosense or faculty that is not strengthened by continual exercise. Thedomestic animal, on the other hand, has food provided for it, issheltered, and often confined, to guard it against the vicissitudes ofthe seasons, is carefully secured from the attacks of its naturalenemies, and seldom even rears its young without human assistance. Halfof its senses and faculties become quite useless, and the other half arebut occasionally called into feeble exercise, while even its muscularsystem is only irregularly brought into action. Now when a variety of such an animal occurs, having increased power orcapacity in any organ or sense, such increase is totally useless, isnever called into action, and may even exist without the animal everbecoming aware of it. In the wild animal, on the contrary, all itsfaculties and powers being brought into full action for the necessitiesof existence, any increase becomes immediately available, isstrengthened by exercise, and must even slightly modify the food, thehabits, and the whole economy of the race. It creates as it were a newanimal, one of superior powers, and which will necessarily increase innumbers and outlive those which are inferior to it. Again, in the domesticated animal all variations have an equal chance ofcontinuance; and those which would decidedly render a wild animal unableto compete with its fellows and continue its existence are nodisadvantage whatever in a state of domesticity. Our quickly fatteningpigs, short-legged sheep pouter pigeons, and poodle dogs could neverhave come into existence in a state of nature, because the very firststep towards such inferior forms would have led to the rapid extinctionof the race; still less could they now exist in competition with theirwild allies. The great speed but slight endurance of the race horse, theunwieldy strength of the ploughman's team, would both be useless in astate of nature. If turned wild on the pampas, such animals wouldprobably soon become extinct, or under favourable circumstances mighteach gradually lose those extreme qualities which would never be calledinto action, and in a few generations revert to a common type, whichmust be that in which the various powers and faculties are soproportioned to each other as to be best adapted to procure food andsecure safety, --that in which by the full exercise of every part of itsorganisation the animal can alone continue to live. Domestic varieties, when turned wild, _must_ return to something near the type of theoriginal wild stock, _or become altogether extinct_. [F] +--------------------------------------------------------------+ | [F] That is, they will vary, and the variations which tend | | to adapt them to the wild state, and therefore approximate | | them to wild animals, will be preserved. Those individuals | | which do not vary sufficiently will perish. | +--------------------------------------------------------------+ We see, then, that no inferences as to the permanence of varieties in astate of nature can be deduced from the observations of those occurringamong domestic animals. The two are so much opposed to each other inevery circumstance of their existence, that what applies to the one isalmost sure not to apply to the other. Domestic animals are abnormal, irregular, artificial; they are subject to variations which never occurand never can occur in a state of nature: their very existence dependsaltogether on human care; so far are many of them removed from that justproportion of faculties, that true balance of organisation, by means ofwhich alone an animal left to its own resources can preserve itsexistence and continue its race. _Lamarck's Hypothesis very different from that now advanced. _ The hypothesis of Lamarck--that progressive changes in species have beenproduced by the attempts of animals to increase the development of theirown organs, and thus modify their structure and habits--has beenrepeatedly and easily refuted by all writers on the subject of varietiesand species, and it seems to have been considered that when this wasdone the whole question has been finally settled; but the view heredeveloped renders such hypothesis quite unnecessary, by showing thatsimilar results must be produced by the action of principles constantlyat work in nature. The powerful retractile talons of the falcon-and thecat-tribes have not been produced or increased by the volition of thoseanimals; but among the different varieties which occurred in the earlierand less highly organized forms of these groups, _those always survivedlongest which had the greatest facilities for seizing their prey_. Neither did the giraffe acquire its long neck by desiring to reach thefoliage of the more lofty shrubs, and constantly stretching its neck forthe purpose, but because any varieties which occurred among itsantitypes with a longer neck than usual _at once secured a fresh rangeof pasture over the same ground as their shorter-necked companions, andon the first scarcity of food were thereby enabled to outlive them_. Even the peculiar colours of many animals, more especially of insects, so closely resembling the soil or leaves or bark on which theyhabitually reside, are explained on the same principle; for though inthe course of ages varieties of many tints may have occurred, _yet thoseraces having colours best adapted to concealment from their enemieswould inevitably survive the longest_. We have also here an acting causeto account for that balance so often observed in nature, --a deficiencyin one set of organs always being compensated by an increaseddevelopment of some others--powerful wings accompanying weak feet, orgreat velocity making up for the absence of defensive weapons; for ithas been shown that all varieties in which an unbalanced deficiencyoccurred could not long continue their existence. The action of thisprinciple is exactly like that of the centrifugal governor of the steamengine, which checks and corrects any irregularities almost before theybecome evident; and in like manner no unbalanced deficiency in theanimal kingdom can ever reach any conspicuous magnitude, because itwould make itself felt at the very first step, by rendering existencedifficult and extinction almost sure soon to follow. An origin such asis here advocated will also agree with the peculiar character of themodifications of form and structure which obtain in organizedbeings--the many lines of divergence from a central type, the increasingefficiency and power of a particular organ through a succession ofallied species, and the remarkable persistence of unimportant parts, such as colour, texture of plumage and hair, form of horns or crests, through a series of species differing considerably in more essentialcharacters. It also furnishes us with a reason for that "morespecialized structure" which Professor Owen states to be acharacteristic of recent compared with extinct forms, and which wouldevidently be the result of the progressive modification of any organapplied to a special purpose in the animal economy. _Conclusion. _ We believe we have now shown that there is a tendency in nature to thecontinued progression of certain classes of _varieties_ further andfurther from the original type--a progression to which there appears noreason to assign any definite limits--and that the same principle whichproduces this result in a state of nature will also explain why domesticvarieties have a tendency, when they become wild, to revert to theoriginal type. This progression, by minute steps, in variousdirections, but always checked and balanced by the necessary conditions, subject to which alone existence can be preserved, may, it is believed, be followed out so as to agree with all the phænomena presented byorganized beings, their extinction and succession in past ages, and allthe extraordinary modifications of form, instinct and habits which theyexhibit. III. MIMICRY, AND OTHER PROTECTIVE RESEMBLANCES AMONG ANIMALS. There is no more convincing proof of the truth of a comprehensivetheory, than its power of absorbing and finding a place for new facts, and its capability of interpreting phænomena which had been previouslylooked upon as unaccountable anomalies. It is thus that the law ofuniversal gravitation and the undulatory theory of light have becomeestablished and universally accepted by men of science. Fact after facthas been brought forward as being apparently inconsistent with them, andone after another these very facts have been shown to be theconsequences of the laws they were at first supposed to disprove. Afalse theory will never stand this test. Advancing knowledge brings tolight whole groups of facts which it cannot deal with, and its advocatessteadily decrease in numbers, notwithstanding the ability and scientificskill with which it may have been supported. The great name of EdwardForbes did not prevent his theory of "Polarity in the distribution ofOrganic beings in Time" from dying a natural death; but the moststriking illustration of the behaviour of a false theory is to be foundin the "Circular and Quinarian System" of classification propounded byMacLeay, and developed by Swainson, with an amount of knowledge andingenuity that have rarely been surpassed. This theory was eminentlyattractive, both from its symmetry and completeness, and from theinteresting nature of the varied analogies and affinities which itbrought to light and made use of. The series of Natural History volumesin "Lardner's Cabinet Cyclopædia, " in which Mr. Swainson developed it inmost departments of the animal kingdom, made it widely known; and infact for a long time these were the best and almost the only populartext-books for the rising generation of naturalists. It was favourablyreceived too by the older school, which was perhaps rather an indicationof its unsoundness. A considerable number of well-known naturalistseither spoke approvingly of it, or advocated similar principles, and fora good many years it was decidedly in the ascendent. With such afavourable introduction, and with such talented exponents, it must havebecome established if it had had any germ of truth in it; yet it quitedied out in a few short years, its very existence is now a matter ofhistory; and so rapid was its fall that its talented creator, Swainson, perhaps lived to be the last man who believed in it. Such is the course of a false theory. That of a true one is verydifferent, as may be well seen by the progress of opinion on the subjectof Natural Selection. In less than eight years "The Origin of Species"has produced conviction in the minds of a majority of the most eminentliving men of science. New facts, new problems, new difficulties as theyarise are accepted, solved or removed by this theory; and its principlesare illustrated by the progress and conclusions of every wellestablished branch of human knowledge. It is the object of the presentessay to show how it has recently been applied to connect together andexplain a variety of curious facts which had long been considered asinexplicable anomalies. _Importance of the Principle of Utility. _ Perhaps no principle has ever been announced so fertile in results asthat which Mr. Darwin so earnestly impresses upon us, and which isindeed a necessary deduction from the theory of Natural Selection, namely--that none of the definite facts of organic nature, no specialorgan, no characteristic form or marking, no peculiarities of instinctor of habit, no relations between species or between groups ofspecies--can exist, but which must now be or once have been _useful_ tothe individuals or the races which possess them. This great principlegives us a clue which we can follow out in the study of many reconditephænomena, and leads us to seek a meaning and a purpose of some definitecharacter in minutiæ which we should be otherwise almost sure to passover as insignificant or unimportant. _Popular Theories of Colour in Animals. _ The adaptation of the external colouring of animals to their conditionsof life has long been recognised, and has been imputed either to anoriginally created specific peculiarity, or to the direct action ofclimate, soil, or food. Where the former explanation has been accepted, it has completely checked inquiry, since we could never get any furtherthan the fact of the adaptation. There was nothing more to be knownabout the matter. The second explanation was soon found to be quiteinadequate to deal with all the varied phases of the phænomena, and tobe contradicted by many well-known facts. For example, wild rabbits arealways of grey or brown tints well suited for concealment among grassand fern. But when these rabbits are domesticated, without any change ofclimate or food, they vary into white or black, and these varieties maybe multiplied to any extent, forming white or black races. Exactly thesame thing has occurred with pigeons; and in the case of rats and mice, the white variety has not been shown to be at all dependent onalteration of climate, food, or other external conditions. In many casesthe wings of an insect not only assume the exact tint of the bark orleaf it is accustomed to rest on, but the form and veining of the leafor the exact rugosity of the bark is imitated; and these detailedmodifications cannot be reasonably imputed to climate or to food, sincein many cases the species does not feed on the substance it resembles, and when it does, no reasonable connexion can be shown to exist betweenthe supposed cause and the effect produced. It was reserved for thetheory of Natural Selection to solve all these problems, and many otherswhich were not at first supposed to be directly connected with them. Tomake these latter intelligible, it will be necessary to give a sketch ofthe whole series of phænomena which may be classed under the head ofuseful or protective resemblances. _Importance of Concealment as Influencing Colour. _ Concealment, more or less complete, is useful to many animals, andabsolutely essential to some. Those which have numerous enemies fromwhich they cannot escape by rapidity of motion, find safety inconcealment. Those which prey upon others must also be so constituted asnot to alarm them by their presence or their approach, or they wouldsoon die of hunger. Now it is remarkable in how many cases nature givesthis boon to the animal, by colouring it with such tints as may bestserve to enable it to escape from its enemies or to entrap its prey. Desert animals as a rule are desert-coloured. The lion is a typicalexample of this, and must be almost invisible when crouched upon thesand or among desert rocks and stones. Antelopes are all more or lesssandy-coloured. The camel is pre-eminently so. The Egyptian cat and thePampas cat are sandy or earth-coloured. The Australian kangaroos are ofthe same tints, and the original colour of the wild horse is supposed tohave been a sandy or clay-colour. The desert birds are still more remarkably protected by theirassimilative hues. The stonechats, the larks, the quails, thegoatsuckers and the grouse, which abound in the North African andAsiatic deserts, are all tinted and mottled so as to resemble withwonderful accuracy the average colour and aspect of the soil in thedistrict they inhabit. The Rev. H. Tristram, in his account of theornithology of North Africa in the 1st volume of the "Ibis, " says: "Inthe desert, where neither trees, brush-wood, nor even undulation of thesurface afford the slightest protection to its foes, a modification ofcolour which shall be assimilated to that of the surrounding country, isabsolutely necessary. Hence _without exception_ the upper plumage of_every bird_, whether lark, chat, sylvain, or sand-grouse, and also thefur of _all the smaller mammals_, and the skin of _all the snakes andlizards_, is of one uniform isabelline or sand colour. " After thetestimony of so able an observer it is unnecessary to adduce furtherexamples of the protective colours of desert animals. Almost equally striking are the cases of arctic animals possessing thewhite colour that best conceals them upon snowfields and icebergs. Thepolar bear is the only bear that is white, and it lives constantly amongsnow and ice. The arctic fox, the ermine and the alpine hare change towhite in winter only, because in summer white would be more conspicuousthan any other colour, and therefore a danger rather than a protection;but the American polar hare, inhabiting regions of almost perpetualsnow, is white all the year round. Other animals inhabiting the sameNorthern regions do not, however, change colour. The sable is a goodexample, for throughout the severity of a Siberian winter it retains itsrich brown fur. But its habits are such that it does not need theprotection of colour, for it is said to be able to subsist on fruits andberries in winter, and to be so active upon the trees as to catch smallbirds among the branches. So also the woodchuck of Canada has adark-brown fur; but then it lives in burrows and frequents river banks, catching fish and small animals that live in or near the water. Among birds, the ptarmigan is a fine example of protective colouring. Its summer plumage so exactly harmonizes with the lichen-coloured stonesamong which it delights to sit, that a person may walk through a flockof them without seeing a single bird; while in winter its white plumageis an almost equal protection. The snow-bunting, the jer-falcon, and thesnowy owl are also white-coloured birds inhabiting the arctic regions, and there can be little doubt but that their colouring is to some extentprotective. Nocturnal animals supply us with equally good illustrations. Mice, rats, bats, and moles possess the least conspicuous of hues, and must be quiteinvisible at times when any light colour would be instantly seen. Owlsand goatsuckers are of those dark mottled tints that will assimilatewith bark and lichen, and thus protect them during the day, and at thesame time be inconspicuous in the dusk. It is only in the tropics, among forests which never lose their foliage, that we find whole groups of birds whose chief colour is green. Theparrots are the most striking example, but we have also a group of greenpigeons in the East; and the barbets, leaf-thrushes, bee-eaters, white-eyes, turacos, and several smaller groups, have so much green intheir plumage as to tend greatly to conceal them among the foliage. _Special Modifications of Colour. _ The conformity of tint which has been so far shown to exist betweenanimals and their habitations is of a somewhat general character; wewill now consider the cases of more special adaptation. If the lion isenabled by his sandy colour readily to conceal himself by merelycrouching down upon the desert, how, it may be asked, do the elegantmarkings of the tiger, the jaguar, and the other large cats agree withthis theory? We reply that these are generally cases of more or lessspecial adaptation. The tiger is a jungle animal, and hides himselfamong tufts of grass or of bamboos, and in these positions the verticalstripes with which his body is adorned must so assimilate with thevertical stems of the bamboo, as to assist greatly in concealing himfrom his approaching prey. How remarkable it is that besides the lionand tiger, almost all the other large cats are arboreal in theirhabits, and almost all have ocellated or spotted skins, which mustcertainly tend to blend them with the background of foliage; while theone exception, the puma, has an ashy brown uniform fur, and has thehabit of clinging so closely to a limb of a tree while waiting for hisprey to pass beneath as to be hardly distinguishable from the bark. Among birds, the ptarmigan, already mentioned, must be considered aremarkable case of special adaptation. Another is a South-Americangoatsucker (Caprimulgus rupestris) which rests in the bright sunshine onlittle bare rocky islets in the Upper Rio Negro, where its unusuallylight colours so closely resemble those of the rock and sand, that itcan scarcely be detected till trodden upon. The Duke of Argyll, in his "Reign of Law, " has pointed out the admirableadaptation of the colours of the woodcock to its protection. The variousbrowns and yellows and pale ash-colour that occur in fallen leaves areall reproduced in its plumage, so that when according to its habit itrests upon the ground under trees, it is almost impossible to detect it. In snipes the colours are modified so as to be equally in harmony withthe prevalent forms and colours of marshy vegetation. Mr. J. M. Lester, in a paper read before the Rugby School Natural History Society, observes:--"The wood-dove, when perched amongst the branches of itsfavourite _fir_, is scarcely discernible; whereas, were it among somelighter foliage, the blue and purple tints in its plumage would farsooner betray it. The robin redbreast too, although it might be thoughtthat the red on its breast made it much easier to be seen, is in realitynot at all endangered by it, since it generally contrives to get amongsome russet or yellow fading leaves, where the red matches very wellwith the autumn tints, and the brown of the rest of the body with thebare branches. " Reptiles offer us many similar examples. The most arboreal lizards, theiguanas, are as green as the leaves they feed upon, and the slenderwhip-snakes are rendered almost invisible as they glide among thefoliage by a similar colouration. How difficult it is sometimes to catchsight of the little green tree-frogs sitting on the leaves of a smallplant enclosed in a glass case in the Zoological Gardens; yet how muchbetter concealed must they be among the fresh green damp foliage of amarshy forest. There is a North-American frog found on lichen-coveredrocks and walls, which is so coloured as exactly to resemble them, andas long as it remains quiet would certainly escape detection. Some ofthe geckos which cling motionless on the trunks of trees in the tropics, are of such curiously marbled colours as to match exactly with the barkthey rest upon. In every part of the tropics there are tree-snakes that twist amongboughs and shrubs, or lie coiled up on the dense masses of foliage. These are of many distinct groups, and comprise both venomous andharmless genera; but almost all of them are of a beautiful greencolour, sometimes more or less adorned with white or dusky bands andspots. There can be little doubt that this colour is doubly useful tothem, since it will tend to conceal them from their enemies, and willlead their prey to approach them unconscious of danger. Dr. Guntherinforms me that there is only one genus of true arboreal snakes (Dipsas)whose colours are rarely green, but are of various shades of black, brown, and olive, and these are all nocturnal reptiles, and there can belittle doubt conceal themselves during the day in holes, so that thegreen protective tint would be useless to them, and they accordinglyretain the more usual reptilian hues. Fishes present similar instances. Many flat fish, as for example theflounder and the skate, are exactly the colour of the gravel or sand onwhich they habitually rest. Among the marine flower gardens of anEastern coral reef the fishes present every variety of gorgeous colour, while the river fish even of the tropics rarely if ever have gay orconspicuous markings. A very curious case of this kind of adaptationoccurs in the sea-horses (Hippocampus) of Australia, some of which bearlong foliaceous appendages resembling seaweed, and are of a brilliantred colour; and they are known to live among seaweed of the same hue, sothat when at rest they must be quite invisible. There are now in theaquarium of the Zoological Society some slender green pipe-fish whichfasten themselves to any object at the bottom by their prehensiletails, and float about with the current, looking exactly like somesimple cylindrical algæ. It is, however, in the insect world that this principle of theadaptation of animals to their environment is most fully and strikinglydeveloped. In order to understand how general this is, it is necessaryto enter somewhat into details, as we shall thereby be better able toappreciate the significance of the still more remarkable phenomena weshall presently have to discuss. It seems to be in proportion to theirsluggish motions or the absence of other means of defence, that insectspossess the protective colouring. In the tropics there are thousands ofspecies of insects which rest during the day clinging to the bark ofdead or fallen trees; and the greater portion of these are delicatelymottled with gray and brown tints, which though symmetrically disposedand infinitely varied, yet blend so completely with the usual colours ofthe bark, that at two or three feet distance they are quiteundistinguishable. In some cases a species is known to frequent only onespecies of tree. This is the case with the common South Americanlong-horned beetle (Onychocerus scorpio) which, Mr. Bates informed me, is found only on a rough-barked tree, called Tapiribá, on the Amazon. Itis very abundant, but so exactly does it resemble the bark in colour andrugosity, and so closely does it cling to the branches, that until itmoves it is absolutely invisible! An allied species (O. Concentricus)is found only at Pará, on a distinct species of tree, the bark of whichit resembles with equal accuracy. Both these insects are abundant, andwe may fairly conclude that the protection they derive from this strangeconcealment is at least one of the causes that enable the race toflourish. Many of the species of Cicindela, or tiger beetle, will illustrate thismode of protection. Our common Cicindela campestris frequents grassybanks, and is of a beautiful green colour, while C. Maritima, which isfound only on sandy sea-shores, is of a pale bronzy yellow, so as to bealmost invisible. A great number of the species found by myself in theMalay islands are similarly protected. The beautiful Cicindela gloriosa, of a very deep velvety green colour, was only taken upon wet mossystones in the bed of a mountain stream, where it was with the greatestdifficulty detected. A large brown species (C. Heros) was found chieflyon dead leaves in forest paths; and one which was never seen except onthe wet mud of salt marshes was of a glossy olive so exactly the colourof the mud as only to be distinguished when the sun shone, by itsshadow! Where the sandy beach was coralline and nearly white, I found avery pale Cicindela; wherever it was volcanic and black, a dark speciesof the same genus was sure to be met with. There are in the East small beetles of the family Buprestidæ whichgenerally rest on the midrib of a leaf, and the naturalist oftenhesitates before picking them off, so closely do they resemble pieces ofbird's dung. Kirby and Spence mention the small beetle Onthophilussulcatus as being like the seed of an umbelliferous plant; and anothersmall weevil, which is much persecuted by predatory beetles of the genusHarpalus, is of the exact colour of loamy soil, and was found to beparticularly abundant in loam pits. Mr. Bates mentions a small beetle(Chlamys pilula) which was undistinguishable by the eye from the dung ofcaterpillars, while some of the Cassidæ, from their hemispherical formsand pearly gold colour, resemble glittering dew-drops upon the leaves. A number of our small brown and speckled weevils at the approach of anyobject roll off the leaf they are sitting on, at the same time drawingin their legs and antennæ, which fit so perfectly into cavities fortheir reception that the insect becomes a mere oval brownish lump, whichit is hopeless to look for among the similarly coloured little stonesand earth pellets among which it lies motionless. The distribution of colour in butterflies and moths respectively is veryinstructive from this point of view. The former have all their brilliantcolouring on the upper surface of all four wings, while the undersurface is almost always soberly coloured, and often very dark andobscure. The moths on the contrary have generally their chief colour onthe hind wings only, the upper wings being of dull, sombre, and oftenimitative tints, and these generally conceal the hind wings when theinsects are in repose. This arrangement of the colours is thereforeeminently protective, because the butterfly always rests with his wingsraised so as to conceal the dangerous brilliancy of his upper surface. It is probable that if we watched their habits sufficiently we shouldfind the under surface of the wings of butterflies very frequentlyimitative and protective. Mr. T. W. Wood has pointed out that the littleorange-tip butterfly often rests in the evening on the green and whiteflower heads of an umbelliferous plant, and that when observed in thisposition the beautiful green and white mottling of the under surfacecompletely assimilates with the flower heads and renders the creaturevery difficult to be seen. It is probable that the rich dark colouringof the under side of our peacock, tortoiseshell, and red-admiralbutterflies answers a similar purpose. Two curious South American butterflies that always settle on the trunksof trees (Gynecia dirce and Callizona acesta) have the under surfacecuriously striped and mottled, and when viewed obliquely must closelyassimilate with the appearance of the furrowed bark of many kinds oftrees. But the most wonderful and undoubted case of protectiveresemblance in a butterfly which I have ever seen, is that of the commonIndian Kallima inachis, and its Malayan ally, Kallima paralekta. Theupper surface of these insects is very striking and showy, as they areof a large size, and are adorned with a broad band of rich orange on adeep bluish ground. The under side is very variable in colour, so thatout of fifty specimens no two can be found exactly alike, but every oneof them will be of some shade of ash or brown or ochre, such as arefound among dead, dry, or decaying leaves. The apex of the upper wingsis produced into an acute point, a very common form in the leaves oftropical shrubs and trees, and the lower wings are also produced into ashort narrow tail. Between these two points runs a dark curved lineexactly representing the midrib of a leaf, and from this radiate on eachside a few oblique lines, which serve to indicate the lateral veins of aleaf. These marks are more clearly seen on the outer portion of the baseof the wings, and on the inner side towards the middle and apex, and itis very curious to observe how the usual marginal and transverse striæof the group are here modified and strengthened so as to become adaptedfor an imitation of the venation of a leaf. We come now to a still moreextraordinary part of the imitation, for we find representations ofleaves in every stage of decay, variously blotched and mildewed andpierced with holes, and in many cases irregularly covered with powderyblack dots gathered into patches and spots, so closely resembling thevarious kinds of minute fungi that grow on dead leaves that it isimpossible to avoid thinking at first sight that the butterfliesthemselves have been attacked by real fungi. But this resemblance, close as it is, would be of little use if thehabits of the insect did not accord with it. If the butterfly sat uponleaves or upon flowers, or opened its wings so as to expose the uppersurface, or exposed and moved its head and antennæ as many otherbutterflies do, its disguise would be of little avail. We might be sure, however, from the analogy of many other cases, that the habits of theinsect are such as still further to aid its deceptive garb; but we arenot obliged to make any such supposition, since I myself had the goodfortune to observe scores of Kallima paralekta, in Sumatra, and tocapture many of them, and can vouch for the accuracy of the followingdetails. These butterflies frequent dry forests and fly very swiftly. They were never seen to settle on a flower or a green leaf, but weremany times lost sight of in a bush or tree of dead leaves. On suchoccasions they were generally searched for in vain, for while gazingintently at the very spot where one had disappeared, it would oftensuddenly dart out, and again vanish twenty or fifty yards further on. Onone or two occasions the insect was detected reposing, and it could thenbe seen how completely it assimilates itself to the surrounding leaves. It sits on a nearly upright twig, the wings fitting closely back toback, concealing the antennæ and head, which are drawn up between theirbases. The little tails of the hind wing touch the branch, and form aperfect stalk to the leaf, which is supported in its place by the clawsof the middle pair of feet, which are slender and inconspicuous. Theirregular outline of the wings gives exactly the perspective effect of ashrivelled leaf. We thus have size, colour, form, markings, and habits, all combining together to produce a disguise which may be said to beabsolutely perfect; and the protection which it affords is sufficientlyindicated by the abundance of the individuals that possess it. The Rev. Joseph Greene has called attention to the striking harmonybetween the colours of those British moths which are on the wing inautumn and winter, and the prevailing tints of nature at those seasons. In autumn various shades of yellow and brown prevail, and he shows thatout of fifty-two species that fly at this season, no less than forty-twoare of corresponding colours. Orgyia antiqua, O. Gonostigma, the generaXanthia, Glæa, and Ennomos are examples. In winter, gray and silverytints prevail, and the genus Chematobia and several species of Hyberniawhich fly during this season are of corresponding hues. No doubt if thehabits of moths in a state of nature were more closely observed, weshould find many cases of special protective resemblance. A few suchhave already been noticed. Agriopis aprilina, Acronycta psi, and manyother moths which rest during the day on the north side of the trunks oftrees can with difficulty be distinguished from the grey and greenlichens that cover them. The lappet moth (Gastropacha querci) closelyresembles both in shape and colour a brown dry leaf; and the well-knownbuff-tip moth, when at rest is like the broken end of a lichen-coveredbranch. There are some of the small moths which exactly resemble thedung of birds dropped on leaves, and on this point Mr. A. Sidgwick, in apaper read before the Rugby School Natural History Society, gives thefollowing original observation:--"I myself have more than once mistakenCilix compressa, a little white and grey moth, for a piece of bird'sdung dropped upon a leaf, and _vice versâ_ the dung for the moth. Bryophila Glandifera and Perla are the very image of the mortar walls onwhich they rest; and only this summer, in Switzerland, I amused myselffor some time in watching a moth, probably Larentia tripunctaria, fluttering about quite close to me, and then alighting on a wall of thestone of the district which it so exactly matched as to be quiteinvisible a couple of yards off. " There are probably hosts of theseresemblances which have not been observed, owing to the difficulty offinding many of the species in their stations of natural repose. Caterpillars are also similarly protected. Many exactly resemble in tintthe leaves they feed upon; others are like little brown twigs, and manyare so strangely marked or humped, that when motionless they can hardlybe taken to be living creatures at all. Mr. Andrew Murray has remarkedhow closely the larva of the peacock moth (Saturnia pavonia-minor)harmonizes in its ground colour with that of the young buds of heatheron which it feeds, and that the pink spots with which it is decoratedcorrespond with the flowers and flower-buds of the same plant. The whole order of Orthoptera, grasshoppers, locusts, crickets, &c. , areprotected by their colours harmonizing with that of the vegetation orthe soil on which they live, and in no other group have we such strikingexamples of special resemblance. Most of the tropical Mantidæ andLocustidæ are of the exact tint of the leaves on which they habituallyrepose, and many of them in addition have the veinings of their wingsmodified so as exactly to imitate that of a leaf. This is carried to thefurthest possible extent in the wonderful genus, Phyllium, the "walkingleaf, " in which not only are the wings perfect imitations of leaves inevery detail, but the thorax and legs are flat, dilated, and leaf-like;so that when tho living insect is resting among the foliage on which itfeeds, the closest observation is often unable to distinguish betweenthe animal and the vegetable. The whole family of the Phasmidæ, or spectres, to which this insectbelongs, is more or less imitative, and a great number of the speciesare called "walking-stick insects, " from their singular resemblance totwigs and branches. Some of these are a foot long and as thick as one'sfinger, and their whole colouring, form, rugosity, and the arrangementof the head, legs, and antennæ, are such as to render them absolutelyidentical in appearance with dead sticks. They hang loosely about shrubsin the forest, and have the extraordinary habit of stretching out theirlegs unsymmetrically, so as to render the deception more complete. Oneof these creatures obtained by myself in Borneo (Ceroxylus laceratus)was covered over with foliaceous excrescences of a clear olive greencolour, so as exactly to resemble a stick grown over by a creeping mossor jungermannia. The Dyak who brought it me assured me it was grown overwith moss although alive, and it was only after a most minuteexamination that I could convince myself it was not so. We need not adduce any more examples to show how important are thedetails of form and of colouring in animals, and that their veryexistence may often depend upon their being by these means concealedfrom their enemies. This kind of protection is found apparently in everyclass and order, for it has been noticed wherever we can obtainsufficient knowledge of the details of an animal's life-history. Itvaries in degree, from the mere absence of conspicuous colour or ageneral harmony with the prevailing tints of nature, up to such a minuteand detailed resemblance to inorganic or vegetable structures as torealize the talisman of the fairy tale, and to give its possessor thepower of rendering itself invisible. _Theory of Protective Colouring. _ We will now endeavour to show how these wonderful resemblances have mostprobably been brought about. Returning to the higher animals, let usconsider the remarkable fact of the rarity of white colouring in themammalia or birds of the temperate or tropical zones in a state ofnature. There is not a single white land-bird or quadruped in Europe, except the few arctic or alpine species, to which white is a protectivecolour. Yet in many of these creatures there seems to be no inherenttendency to avoid white, for directly they are domesticated whitevarieties arise, and appear to thrive as well as others. We have whitemice and rats, white cats, horses, dogs, and cattle, white poultry, pigeons, turkeys, and ducks, and white rabbits. Some of these animalshave been domesticated for a long period, others only for a fewcenturies; but in almost every case in which an animal has beenthoroughly domesticated, parti-coloured and white varieties are producedand become permanent. It is also well known that animals in a state of nature produce whitevarieties occasionally. Blackbirds, starlings, and crows areoccasionally seen white, as well as elephants, deer, tigers, hares, moles, and many other animals; but in no case is a permanent white raceproduced. Now there are no statistics to show that the normal-colouredparents produce white offspring oftener under domestication than in astate of nature, and we have no right to make such an assumption if thefacts can be accounted for without it. But if the colours of animals doreally, in the various instances already adduced, serve for theirconcealment and preservation, then white or any other conspicuous colourmust be hurtful, and must in most cases shorten an animal's life. Awhite rabbit would be more surely the prey of hawk or buzzard, and thewhite mole, or field mouse, could not long escape from the vigilant owl. So, also, any deviation from those tints best adapted to conceal acarnivorous animal would render the pursuit of its prey much moredifficult, would place it at a disadvantage among its fellows, and in atime of scarcity would probably cause it to starve to death. On theother hand, if an animal spreads from a temperate into an arcticdistrict, the conditions are changed. During a large portion of theyear, and just when the struggle for existence is most severe, white isthe prevailing tint of nature, and dark colours will be the mostconspicuous. The white varieties will now have an advantage; they willescape from their enemies or will secure food, while their browncompanions will be devoured or will starve; and as "like produces like"is the established rule in nature, the white race will becomepermanently established, and dark varieties, when they occasionallyappear, will soon die out from their want of adaptation to theirenvironment. In each case the fittest will survive, and a race will beeventually produced adapted to the conditions in which it lives. We have here an illustration of the simple and effectual means by whichanimals are brought into harmony with the rest of nature. That slightamount of variability in every species, which we often look upon assomething accidental or abnormal, or so insignificant as to be hardlyworthy of notice, is yet the foundation of all those wonderful andharmonious resemblances which play such an important part in the economyof nature. Variation is generally very small in amount, but it is allthat is required, because the change in the external conditions to whichan animal is subject is generally very slow and intermittent. When thesechanges have taken place too rapidly, the result has often been theextinction of species; but the general rule is, that climatal andgeological changes go on slowly, and the slight but continualvariations in the colour, form, and structure of all animals, hasfurnished individuals adapted to these changes, and who have become theprogenitors of modified races. Rapid multiplication, incessant slightvariation, and survival of the fittest--these are the laws which everkeep the organic world in harmony with the inorganic, and with itself. These are the laws which we believe have produced all the cases ofprotective resemblance already adduced, as well as those still morecurious examples we have yet to bring before our readers. It must always be borne in mind that the more wonderful examples, inwhich there is not only a general but a special resemblance--as in thewalking leaf, the mossy phasma, and the leaf-winged butterfly--representthose few instances in which the process of modification has been goingon during an immense series of generations. They all occur in thetropics, where the conditions of existence are the most favourable, andwhere climatic changes have for long periods been hardly perceptible. Inmost of them favourable variations both of colour, form, structure, andinstinct or habit, must have occurred to produce the perfect adaptationwe now behold. All these are known to vary, and favourable variationswhen not accompanied by others that were unfavourable, would certainlysurvive. At one time a little step might be made in this direction, atanother time in that--a change of conditions might sometimes renderuseless that which it had taken ages to produce--great and suddenphysical modifications might often produce the extinction of a racejust as it was approaching perfection, and a hundred checks of which wecan know nothing may have retarded the progress towards perfectadaptation; so that we can hardly wonder at there being so few cases inwhich a completely successful result has been attained as shown by theabundance and wide diffusion of the creatures so protected. _Objection that Colour, as being dangerous, should not exist in Nature. _ It is as well here to reply to an objection that will no doubt occur tomany readers--that if protection is so useful to all animals, and soeasily brought about by variation and survival of the fittest, thereought to be no conspicuously-coloured creatures; and they will perhapsask how we account for the brilliant birds, and painted snakes, andgorgeous insects, that occur abundantly all over the world. It will beadvisable to answer this question rather fully, in order that we may beprepared to understand the phenomena of "mimicry, " which it is thespecial object of this paper to illustrate and explain. The slightest observation of the life of animals will show us, that theyescape from their enemies and obtain their food in an infinite number ofways; and that their varied habits and instincts are in every caseadapted to the conditions of their existence. The porcupine and thehedgehog have a defensive armour that saves them from the attacks ofmost animals. The tortoise is not injured by the conspicuous colours ofhis shell, because that shell is in most cases an effectual protectionto him. The skunks of North America find safety in their power ofemitting an unbearably offensive odour; the beaver in its aquatic habitsand solidly constructed abode. In some cases the chief danger to ananimal occurs at one particular period of its existence, and if that isguarded against its numbers can easily be maintained. This is the casewith many birds, the eggs and young of which are especially obnoxious todanger, and we find accordingly a variety of curious contrivances toprotect them. We have nests carefully concealed, hung from the slenderextremities of grass or boughs over water, or placed in the hollow of atree with a very small opening. When these precautions are successful, so many more individuals will be reared than can possibly find foodduring the least favourable seasons, that there will always be a numberof weakly and inexperienced young birds who will fall a prey to theenemies of the race, and thus render necessary for the stronger andhealthier individuals no other safeguard than their strength andactivity. The instincts most favourable to the production and rearing ofoffspring will in these cases be most important, and the survival of thefittest will act so as to keep up and advance those instincts, whileother causes which tend to modify colour and marking may continue theiraction almost unchecked. It is perhaps in insects that we may best study the varied means bywhich animals are defended or concealed. One of the uses of thephosphorescence with which many insects are furnished, is probably tofrighten away their enemies; for Kirby and Spence state that a groundbeetle (Carabus) has been observed running round and round a luminouscentipede as if afraid to attack it. An immense number of insects havestings, and some stingless ants of the genus Polyrachis are armed withstrong and sharp spines on the back, which must render them unpalatableto many of the smaller insectivorous birds. Many beetles of the familyCurculionidæ have the wing cases and other external parts so excessivelyhard, that they cannot be pinned without first drilling a hole toreceive the pin, and it is probable that all such find a protection inthis excessive hardness. Great numbers of insects hide themselves amongthe petals of flowers, or in the cracks of bark and timber; and finally, extensive groups and even whole orders have a more or less powerful anddisgusting smell and taste, which they either possess permanently, orcan emit at pleasure. The attitudes of some insects may also protectthem, as the habit of turning up the tail by the harmless rove-beetles(Staphylindidæ) no doubt leads other animals besides children to thebelief that they can sting. The curious attitude assumed by sphinxcaterpillars is probably a safeguard, as well as the blood-red tentacleswhich can suddenly be thrown out from the neck, by the caterpillars ofall the true swallow-tailed butterflies. It is among the groups that possess some of these varied kinds ofprotection in a high degree, that we find the greatest amount ofconspicuous colour, or at least the most complete absence of protectiveimitation. The stinging Hymenoptera, wasps, bees, and hornets, are, as arule, very showy and brilliant insects, and there is not a singleinstance recorded in which any one of them is coloured so as to resemblea vegetable or inanimate substance. The Chrysididæ, or golden wasps, which do not sting, possess as a substitute the power of rollingthemselves up into a ball, which is almost as hard and polished as ifreally made of metal, --and they are all adorned with the most gorgeouscolours. The whole order Hemiptera (comprising the bugs) emit a powerfulodour, and they present a very large proportion of gay-coloured andconspicuous insects. The lady-birds (Coccinellidæ) and their allies theEumorphidæ, are often brightly spotted, as if to attract attention; butthey can both emit fluids of a very disagreeable nature, they arecertainly rejected by some birds, and are probably never eaten by any. The great family of ground beetles (Carabidæ) almost all possess adisagreeable and some a very pungent smell, and a few, called bombardierbeetles, have the peculiar faculty of emitting a jet of very volatileliquid, which appears like a puff of smoke, and is accompanied by adistinct crepitating explosion. It is probably because these insects aremostly nocturnal and predacious that they do not present more vividhues. They are chiefly remarkable for brilliant metallic tints or dullred patches when they are not wholly black, and are therefore veryconspicuous by day, when insect-eaters are kept off by their bad odourand taste, but are sufficiently invisible at night when it is ofimportance that their prey should not become aware of their proximity. It seems probable that in some cases that which would appear at first tobe a source of danger to its possessor may really be a means ofprotection. Many showy and weak-flying butterflies have a very broadexpanse of wing, as in the brilliant blue Morphos of Brazilian forests, and the large Eastern Papilios; yet these groups are tolerablyplentiful. Now, specimens of these butterflies are often captured withpierced and broken wings, as if they had been seized by birds from whomthey had escaped; but if the wings had been much smaller in proportionto the body, it seems probable that the insect would be more frequentlystruck or pierced in a vital part, and thus the increased expanse of thewings may have been indirectly beneficial. In other cases the capacity of increase in a species is so great thathowever many of the perfect insect may be destroyed, there is alwaysample means for the continuance of the race. Many of the flesh flies, gnats, ants, palm-tree weevils and locusts are in this category. Thewhole family of Cetoniadæ or rose chafers, so full of gaily-colouredspecies, are probably saved from attack by a combination of characters. They fly very rapidly with a zigzag or waving course; they hidethemselves the moment they alight, either in the corolla of flowers, orin rotten wood, or in cracks and hollows of trees, and they aregenerally encased in a very hard and polished coat of mail which mayrender them unsatisfactory food to such birds as would be able tocapture them. The causes which lead to the development of colour havebeen here able to act unchecked, and we see the result in a largevariety of the most gorgeously-coloured insects. Here, then, with our very imperfect knowledge of the life-history ofanimals, we are able to see that there are widely varied modes by whichthey may obtain protection from their enemies or concealment from theirprey. Some of those seem to be so complete and effectual as to answerall the wants of the race, and lead to the maintenance of the largestpossible population. When this is the case, we can well understand thatno further protection derived from a modification of colour can be ofthe slightest use, and the most brilliant hues may be developed withoutany prejudicial effect upon the species. On some of the laws thatdetermine the development of colour something may be said presently. Itis now merely necessary to show that concealment by obscure or imitativetints is only one out of very many ways by which animals maintain theirexistence; and having done this we are prepared to consider thephenomena of what has been termed "mimicry. " It is to be particularlyobserved, however, that the word is not here used in the sense ofvoluntary imitation, but to imply a particular kind of resemblance--aresemblance not in internal structure but in external appearance--aresemblance in those parts only that catch the eye--a resemblance thatdeceives. As this kind of resemblance has the same effect as voluntaryimitation or mimicry, and as we have no word that expresses the requiredmeaning, "mimicry" was adopted by Mr. Bates (who was the first toexplain the facts), and has led to some misunderstanding; but there needbe none, if it is remembered that both "mimicry" and "imitation" areused in a metaphorical sense, as implying that close external likenesswhich causes things unlike in structure to be mistaken for each other. _Mimicry. _ It has been long known to entomologists that certain insects bear astrange external resemblance to others belonging to distinct genera, families, or even orders, and with which they have no real affinitywhatever. The fact, however, appears to have been generally consideredas dependent upon some unknown law of "analogy"--some "system ofnature, " or "general plan, " which had guided the Creator in designingthe myriads of insect forms, and which we could never hope tounderstand. In only one case does it appear that the resemblance wasthought to be useful, and to have been designed as a means to a definiteand intelligible purpose. The flies of the genus Volucella enter thenests of bees to deposit their eggs, so that their larvæ may feed uponthe larvæ of the bees, and these flies are each wonderfully like the beeon which it is parasitic. Kirby and Spence believed that thisresemblance or "mimicry" was for the express purpose of protecting theflies from the attacks of the bees, and the connection is so evidentthat it was hardly possible to avoid this conclusion. The resemblance, however, of moths to butterflies or to bees, of beetles to wasps, and oflocusts to beetles, has been many times noticed by eminent writers; butscarcely ever till within the last few years does it appear to have beenconsidered that these resemblances had any special purpose, or were ofany direct benefit to the insects themselves. In this respect they werelooked upon as accidental, as instances of the "curious analogies" innature which must be wondered at but which could not be explained. Recently, however, these instances have been greatly multiplied; thenature of the resemblances has been more carefully studied, and it hasbeen found that they are often carried out into such details as almostto imply a purpose of deceiving the observer. The phenomena, moreover, have been shown to follow certain definite laws, which again allindicate their dependence on the more general law of the "survival ofthe fittest, " or "the preservation of favoured races in the struggle forlife. " It will, perhaps, be as well here to state what these laws orgeneral conclusions are, and then to give some account of the factswhich support them. The first law is, that in an overwhelming majority of cases of mimicry, the animals (or the groups) which resemble each other inhabit the samecountry, the same district, and in most cases are to be found togetheron the very same spot. The second law is, that these resemblances are not indiscriminate, butare limited to certain groups, which in every case are abundant inspecies and individuals, and can often be ascertained to have somespecial protection. The third law is, that the species which resemble or "mimic" thesedominant groups, are comparatively less abundant in individuals, and areoften very rare. These laws will be found to hold good, in all the cases of true mimicryamong various classes of animals to which we have now to call theattention of our readers. _Mimicry among Lepidoptera. _ As it is among butterflies that instances of mimicry are most numerousand most striking, an account of some of the more prominent examples inthis group will first be given. There is in South America an extensivefamily of these insects, the Heliconidæ, which are in many respects veryremarkable. They are so abundant and characteristic in all the woodyportions of the American tropics, that in almost every locality theywill be seen more frequently than any other butterflies. They aredistinguished by very elongate wings, body, and antennæ, and areexceedingly beautiful and varied in their colours; spots and patches ofyellow, red, or pure white upon a black, blue, or brown ground, beingmost general. They frequent the forests chiefly, and all fly slowly andweakly; yet although they are so conspicuous, and could certainly becaught by insectivorous birds more easily than almost any otherinsects, their great abundance all over the wide region they inhabitshows that they are not so persecuted. It is to be especially remarkedalso, that they possess no adaptive colouring to protect them duringrepose, for the under side of their wings presents the same, or at leastan equally conspicuous colouring as the upper side; and they may beobserved after sunset suspended at the end of twigs and leaves wherethey have taken up their station for the night, fully exposed to theattacks of enemies if they have any. These beautiful insects possess, however, a strong pungent semi-aromatic or medicinal odour, which seemsto pervade all the juices of their system. When the entomologistsqueezes the breast of one of them between his fingers to kill it, ayellow liquid exudes which stains the skin, and the smell of which canonly be got rid of by time and repeated washings. Here we have probablythe cause of their immunity from attack, since there is a great deal ofevidence to show that certain insects are so disgusting to birds thatthey will under no circumstances touch them. Mr. Stainton has observedthat a brood of young turkeys greedily devoured all the worthless mothshe had amassed in a night's "sugaring, " yet one after another seized andrejected a single white moth which happened to be among them. Youngpheasants and partridges which eat many kinds of caterpillars seem tohave an absolute dread of that of the common currant moth, which theywill never touch, and tomtits as well as other small birds appear neverto eat the same species. In the case of the Heliconidæ, however, wehave some direct evidence to the same effect. In the Brazilian foreststhere are great numbers of insectivorous birds--as jacamars, trogons, and puffbirds--which catch insects on the wing, and that they destroymany butterflies is indicated by the fact that the wings of theseinsects are often found on the ground where their bodies have beendevoured. But among these there are no wings of Heliconidæ, while thoseof the large showy Nymphalidæ, which have a much swifter flight, areoften met with. Again, a gentleman who had recently returned from Brazilstated at a meeting of the Entomological Society that he once observed apair of puffbirds catching butterflies, which they brought to their nestto feed their young; yet during half an hour they never brought one ofthe Heliconidæ, which were flying lazily about in great numbers, andwhich they could have captured more easily than any others. It was thiscircumstance that led Mr. Belt to observe them so long, as he could notunderstand why the most common insects should be altogether passed by. Mr. Bates also tells us that he never saw them molested by lizards orpredacious flies, which often pounce on other butterflies. If, therefore, we accept it as highly probable (if not proved) that theHeliconidæ are very greatly protected from attack by their peculiarodour and taste, we find it much more easy to understand their chiefcharacteristics--their great abundance, their slow flight, their gaudycolours, and the entire absence of protective tints on their undersurfaces. This property places them somewhat in the position of thosecurious wingless birds of oceanic islands, the dodo, the apteryx, andthe moas, which are with great reason supposed to have lost the power offlight on account of the absence of carnivorous quadrupeds. Ourbutterflies have been protected in a different way, but quite aseffectually; and the result has been that as there has been nothing toescape from, there has been no weeding out of slow flyers, and as therehas been nothing to hide from, there has been no extermination of thebright-coloured varieties, and no preservation of such as tended toassimilate with surrounding objects. Now let us consider how this kind of protection must act. Tropicalinsectivorous birds very frequently sit on dead branches of a loftytree, or on those which overhang forest paths, gazing intently around, and darting off at intervals to seize an insect at a considerabledistance, which they generally return to their station to devour. If abird began by capturing the slow-flying, conspicuous Heliconidæ, andfound them always so disagreeable that it could not eat them, it wouldafter a very few trials leave off catching them at all; and their wholeappearance, form, colouring, and mode of flight is so peculiar, thatthere can be little doubt birds would soon learn to distinguish them ata long distance, and never waste any time in pursuit of them. Underthese circumstances, it is evident that any other butterfly of a groupwhich birds were accustomed to devour, would be almost equally wellprotected by closely resembling a Heliconia externally, as if itacquired also the disagreeable odour; always supposing that there wereonly a few of them among a great number of the Heliconias. If the birdscould not distinguish the two kinds externally, and there were on theaverage only one eatable among fifty uneatable, they would soon give upseeking for the eatable ones, even if they knew them to exist. If, onthe other hand, any particular butterfly of an eatable group acquiredthe disagreeable taste of the Heliconias while it retained thecharacteristic form and colouring of its own group, this would be reallyof no use to it whatever; for the birds would go on catching it amongits eatable allies (compared with which it would rarely occur), it wouldbe wounded and disabled, even if rejected, and its increase would thusbe as effectually checked as if it were devoured. It is important, therefore, to understand that if any one genus of an extensive family ofeatable butterflies were in danger of extermination from insect-eatingbirds, and if two kinds of variation were going on among them, someindividuals possessing a slightly disagreeable taste, others a slightresemblance to the Heliconidæ, this latter quality would be much morevaluable than the former. The change in flavour would not at all preventthe variety from being captured as before, and it would almost certainlybe thoroughly disabled before being rejected. The approach in colour andform to the Heliconidæ, however, would be at the very first a positive, though perhaps a slight advantage; for although at short distances thisvariety would be easily distinguished and devoured, yet at a longerdistance it might be mistaken for one of the uneatable group, and so bepassed by and gain another day's life, which might in many cases besufficient for it to lay a quantity of eggs and leave a numerousprogeny, many of which would inherit the peculiarity which had been thesafeguard of their parent. Now, this hypothetical case is exactly realized in South America. Amongthe white butterflies forming the family Pieridæ (many of which do notgreatly differ in appearance from our own cabbage butterflies) is agenus of rather small size (Leptalis), some species of which are whitelike their allies, while the larger number exactly resemble theHeliconidæ in the form and colouring of the wings. It must always beremembered that these two families are as absolutely distinguished fromeach other by structural characters as are the carnivora and theruminants among quadrupeds, and that an entomologist can alwaysdistinguish the one from the other by the structure of the feet, just ascertainly as a zoologist can tell a bear from a buffalo by the skull orby a tooth. Yet the resemblance of a species of the one family toanother species in the other family was often so great, that both Mr. Bates and myself were many times deceived at the time of capture, anddid not discover the distinctness of the two insects till a closerexamination detected their essential differences. During his residenceof eleven years in the Amazon valley, Mr. Bates found a number ofspecies or varieties of Leptalis, each of which was a more or less exactcopy of one of the Heliconidæ of the district it inhabited; and theresults of his observations are embodied in a paper published in theLinnean Transactions, in which he first explained the phenomena of"mimicry" as the result of natural selection, and showed its identity incause and purpose with protective resemblance to vegetable or inorganicforms. The imitation of the Heliconidæ by the Leptalides is carried out to awonderful degree in form as well as in colouring. The wings have becomeelongated to the same extent, and the antennæ and abdomen have bothbecome lengthened, to correspond with the unusual condition in whichthey exist in the former family. In colouration there are several typesin the different genera of Heliconidæ. The genus Mechanitis is generallyof a rich semi-transparent brown, banded with black and yellow; Methonais of large size, the wings transparent like horn, and with blacktransverse bands; while the delicate Ithomias are all more or lesstransparent, with black veins and borders, and often with marginal andtransverse bands of orange red. These different forms are all copied bythe various species of Leptalis, every band and spot and tint of colour, and the various degrees of transparency, being exactly reproduced. As ifto derive all the benefit possible from this protective mimicry, thehabits have become so modified that the Leptalides generally frequentthe very same spots as their models, and have the same mode of flight;and as they are always very scarce (Mr. Bates estimating their numbersat about one to a thousand of the group they resemble), there is hardlya possibility of their being found out by their enemies. It is alsovery remarkable that in almost every case the particular Ithomias andother species of Heliconidæ which they resemble, are noted as being verycommon species, swarming in individuals, and found over a wide range ofcountry. This indicates antiquity and permanence in the species, and isexactly the condition most essential both to aid in the development ofthe resemblance, and to increase its utility. But the Leptalides are not the only insects who have prolonged theirexistence by imitating the great protected group of Heliconidæ;--a genusof quite another family of most lovely small American butterflies, theErycinidæ, and three genera of diurnal moths, also present species whichoften mimic the same dominant forms, so that some, as Ithomia ilerdinaof St. Paulo, for instance, have flying with them a few individuals ofthree widely different insects, which are yet disguised with exactly thesame form, colour, and markings, so as to be quite undistinguishablewhen upon the wing. Again, the Heliconidæ are not the only group thatare imitated, although they are the most frequent models. The black andred group of South American Papilios, and the handsome Erycinian genusStalachtis, have also a few who copy them; but this fact offers nodifficulty, since these two groups are almost as dominant as theHeliconidæ. They both fly very slowly, they are both conspicuouslycoloured, and they both abound in individuals; so that there is everyreason to believe that they possess a protection of a similar kind tothe Heliconidæ, and that it is therefore equally an advantage to otherinsects to be mistaken for them. There is also another extraordinaryfact that we are not yet in a position clearly to comprehend: somegroups of the Heliconidæ themselves mimic other groups. Species ofHeliconia mimic Mechanitis, and every species of Napeogenes mimics someother Heliconideous butterfly. This would seem to indicate that thedistasteful secretion is not produced alike by all members of thefamily, and that where it is deficient protective imitation comes intoplay. It is this, perhaps, that has caused such a general resemblanceamong the Heliconidæ, such a uniformity of type with great diversity ofcolouring, since any aberration causing an insect to cease to look likeone of the family would inevitably lead to its being attacked, wounded, and exterminated, even although it was not eatable. In other parts of the world an exactly parallel series of facts havebeen observed. The Danaidæ and the Acræidæ of the Old World tropics formin fact one great group with the Heliconidæ. They have the same generalform, structure, and habits: they possess the same protective odour, andare equally abundant in individuals, although not so varied in colour, blue and white spots on a black ground being the most general pattern. The insects which mimic these are chiefly Papilios, and Diadema, a genusallied to our peacock and tortoiseshell butterflies. In tropical Africathere is a peculiar group of the genus Danais, characterized bydark-brown and bluish-white colours, arranged in bands or stripes. Oneof these, Danais niavius, is exactly imitated both by Papilio hippocoonand by Diadema anthedon; another, Danais echeria, by Papilio cenea; andin Natal a variety of the Danais is found having a white spot at the tipof wings, accompanied by a variety of the Papilio bearing acorresponding white spot. Acræa gea is copied in its very peculiar styleof colouration by the female of Papilio cynorta, by Panopæa hirce, andby the female of Elymnias phegea. Acræa euryta of Calabar has a femalevariety of Panopea hirce from the same place which exactly copies it;and Mr. Trimen, in his paper on Mimetic Analogies among AfricanButterflies, published in the Transactions of the Linnæan Society for1868, gives a list of no less than sixteen species and varieties ofDiadema and its allies, and ten of Papilio, which in their colour andmarkings are perfect mimics of species or varieties of Danais or Acræawhich inhabit the same districts. Passing on to India, we have Danais tytia, a butterfly withsemi-transparent bluish wings and a border of rich reddish brown. Thisremarkable style of colouring is exactly reproduced in Papilio agestorand in Diadema nama, and all three insects not unfrequently cometogether in collections made at Darjeeling. In the Philippine Islandsthe large and curious Idea leuconöe with its semi-transparent whitewings, veined and spotted with black, is copied by the rare Papilioidæoides from the same islands. In the Malay archipelago the very common and beautiful Euploea midamusis so exactly mimicked by two rare Papilios (P. Paradoxa and P. ænigma)that I generally caught them under the impression that they were themore common species; and the equally common and even more beautifulEuploea rhadamanthus, with its pure white bands and spots on a ground ofglossy blue and black, is reproduced in the Papilio caunus. Here alsothere are species of Diadema imitating the same group in two or threeinstances; but we shall have to adduce these further on in connexionwith another branch of the subject. It has been already mentioned that in South America there is a group ofPapilios which have all the characteristics of a protected race, andwhose peculiar colours and markings are imitated by other butterfliesnot so protected. There is just such a group also in the East, havingvery similar colours and the same habits, and these also are mimicked byother species in the same genus not closely allied to them, and also bya few of other families. Papilio hector, a common Indian butterfly of arich black colour spotted with crimson, is so closely copied by Papilioromulus, that the latter insect has been thought to be its female. Aclose examination shows, however, that it is essentially different, andbelongs to another section of the genus. Papilio antiphus and P. Diphilus, black swallow-tailed butterflies with cream-coloured spots, are so well imitated by varieties of P. Theseus, that several writershave classed them as the same species. Papilio liris, found only in theisland of Timor, is accompanied there by P. ænomaus, the female ofwhich so exactly resembles it that they can hardly be separated in thecabinet, and on the wing are quite undistinguishable. But one of themost curious cases is the fine yellow-spotted Papilio cöon, which isunmistakeably imitated by the female tailed form of Papilio memnon. These are both from Sumatra; but in North India P. Cöon is replaced byanother species, which has been named P. Doubledayi, having red spotsinstead of yellow; and in the same district the corresponding femaletailed form of Papilio androgeus, sometimes considered a variety of P. Memnon, is similarly red-spotted. Mr. Westwood has described somecurious day-flying moths (Epicopeia) from North India, which have theform and colour of Papilios of this section, and two of these are verygood imitations of Papilio polydorus and Papilio varuna, also from NorthIndia. Almost all these cases of mimicry are from the tropics, where the formsof life are more abundant, and where insect development especially is ofunchecked luxuriance; but there are also one or two instances intemperate regions. In North America, the large and handsome red andblack butterfly Danais erippus is very common; and the same country isinhabited by Limenitis archippus, which closely resembles the Danais, while it differs entirely from every species of its own genus. The only case of probable mimicry in our own country is thefollowing:--A very common white moth (Spilosoma menthastri) was found byMr. Stainton to be rejected by young turkeys among hundreds of othermoths on which they greedily fed. Each bird in succession took hold ofthis moth and threw it down again, as if too nasty to eat. Mr. JennerWeir also found that this moth was refused by the Bullfinch, Chaffinch, Yellow Hammer, and Red Bunting, but eaten after much hesitation by theRobin. We may therefore fairly conclude that this species would bedisagreeable to many other birds, and would thus have an immunity fromattack, which may be the cause of its great abundance and of itsconspicuous white colour. Now it is a curious thing that there isanother moth, Diaphora mendica, which appears about the same time, andwhose female only is white. It is about the same size as Spilosomamenthastri, and sufficiently resembles it in the dusk, and this moth ismuch less common. It seems very probable, therefore, that these speciesstand in the same relation to each other as the mimicking butterflies ofvarious families do to the Heliconidæ and Danaidæ. It would be veryinteresting to experiment on all white moths, to ascertain if thosewhich are most common are generally rejected by birds. It may beanticipated that they would be so, because white is the most conspicuousof all colours for nocturnal insects, and had they not some otherprotection would certainly be very injurious to them. _Lepidoptera mimicking other Insects. _ In the preceding cases we have found Lepidoptera imitating other speciesof the same order, and such species only as we have good reason tobelieve were free from the attacks of many insectivorous creatures; butthere are other instances in which they altogether lose the externalappearance of the order to which they belong, and take on the dress ofbees or wasps--insects which have an undeniable protection in theirstings. The Sesiidæ and Ægeriidæ, two families of day-flying moths, areparticularly remarkable in this respect, and a mere inspection of thenames given to the various species shows how the resemblance has struckeveryone. We have apiformis, vespiforme, ichneumoniforme, scoliæforme, sphegiforme (bee-like, wasp-like, ichneumon-like, &c. ) and many others, all indicating a resemblance to stinging Hymenoptera. In Britain we mayparticularly notice Sesia bombiliformis, which very closely resemblesthe male of the large and common humble bee, Bombus hortorum; Spheciacraboniforme, which is coloured like a hornet, and is (on the authorityof Mr. Jenner Weir) much more like it when alive than when in thecabinet, from the way in which it carries its wings; and the currantclear-wing, Trochilium tipuliforme, which resembles a small black wasp(Odynerus sinuatus) very abundant in gardens at the same season. It hasbeen so much the practice to look upon these resemblances as merecurious analogies playing no part in the economy of nature, that we havescarcely any observations of the habits and appearance when alive of thehundreds of species of these groups in various parts of the world, orhow far they are accompanied by Hymenoptera, which they specificallyresemble. There are many species in India (like those figured byProfessor Westwood in his "Oriental Entomology") which have the hindlegs very broad and densely hairy, so as exactly to imitate thebrush-legged bees (Scopulipedes) which abound in the same country. Inthis case we have more than mere resemblance of colour, for that whichis an important functional structure in the one group is imitated inanother whose habits render it perfectly useless. _Mimicry among Beetles. _ It may fairly be expected that if these imitations of one creature byanother really serve as a protection to weak and decaying species, instances of the same kind will be found among other groups than theLepidoptera; and such is the case, although they are seldom so prominentand so easily recognised as those already pointed out as occurring inthat order. A few very interesting examples may, however, be pointed outin most of the other orders of insects. The Coleoptera or beetles thatimitate other Coleoptera of distinct groups are very numerous intropical countries, and they generally follow the laws already laid downas regulating these phenomena. The insects which others imitate alwayshave a special protection, which leads them to be avoided as dangerousor uneatable by small insectivorous animals; some have a disgustingtaste (analogous to that of the Heliconidæ); others have such a hard andstony covering that they cannot be crushed or digested; while a thirdset are very active, and armed with powerful jaws, as well as havingsome disagreeable secretion. Some species of Eumorphidæ and Hispidæ, small flat or hemispherical beetles which are exceedingly abundant, andhave a disagreeable secretion, are imitated by others of the verydistinct group of Longicornes (of which our common musk-beetle may betaken as an example). The extraordinary little Cyclopeplus batesii, belongs to the same sub-family of this group as the Onychocerus scorpioand O. Concentricus, which have already been adduced as imitating withsuch wonderful accuracy the bark of the trees they habitually frequent;but it differs totally in outward appearance from every one of itsallies, having taken upon itself the exact shape and colouring of aglobular Corynomalus, a little stinking beetle with clubbed antennæ. Itis curious to see how these clubbed antennæ are imitated by an insectbelonging to a group with long slender antennæ. The sub-familyAnisocerinæ, to which Cyclopeplus belongs, is characterised by all itsmembers possessing a little knob or dilatation about the middle of theantennæ. This knob is considerably enlarged in C. Batesii, and theterminal portion of the antennæ beyond it is so small and slender as tobe scarcely visible, and thus an excellent substitute is obtained forthe short clubbed antennæ of the Corynomalus. Erythroplatis coralliferis another curious broad flat beetle, that no one would take for aLongicorn, since it almost exactly resembles Cephalodonta spinipes, oneof the commonest of the South American Hispidæ; and what is still moreremarkable, another Longicorn of a distinct group, Streptolabishispoides, was found by Mr. Bates, which resembles the same insect withequal minuteness, --a case exactly parallel to that among butterflies, where species of two or three distinct groups mimicked the sameHeliconia. Many of the soft-winged beetles (Malacoderms) are excessivelyabundant in individuals, and it is probable that they have some similarprotection, more especially as other species often strikingly resemblethem. A Longicorn beetle, Pæciloderma terminale, found in Jamaica, iscoloured exactly in the same way as a Lycus (one of the Malacoderms)from the same island. Eroschema poweri, a Longicorn from Australia, might certainly be taken for one of the same group, and several speciesfrom the Malay Islands are equally deceptive. In the Island of Celebes Ifound one of this group, having the whole body and elytra of a rich deepblue colour, with the head only orange; and in company with it an insectof a totally different family (Eucnemidæ) with identically the samecolouration, and of so nearly the same size and form as to completelypuzzle the collector on every fresh occasion of capturing them. I havebeen recently informed by Mr. Jenner Weir, who keeps a variety of smallbirds, that none of them will touch our common "soldiers and sailors"(species of Malacoderms), thus confirming my belief that they were aprotected group, founded on the fact of their being at once veryabundant, of conspicuous colours, and the objects of mimicry. There are a number of the larger tropical weevils which have theelytra and the whole covering of the body so hard as to be a greatannoyance to the entomologist, because in attempting to transfix themthe points of his pins are constantly turned. I have found it necessaryin these cases to drill a hole very carefully with the point of asharp penknife before attempting to insert a pin. Many of the finelong-antennæd Anthribidæ (an allied group) have to be treated in thesame way. We can easily understand that after small birds have in vainattempted to eat these insects, they should get to know them by sight, and ever after leave them alone, and it will then be an advantage forother insects which are comparatively soft and eatable, to be mistakenfor them. We need not be surprised, therefore, to find that there aremany Longicorns which strikingly resemble the "hard beetles" of theirown district. In South Brazil, Acanthotritus dorsalis is strikinglylike a Curculio of the hard genus Heiliplus, and Mr. Bates assures methat he found Gymnocerus cratosomoides (a Longicorn) on the same treewith a hard Cratosomus (a weevil), which it exactly mimics. Again, thepretty Longicorn, Phacellocera batesii, mimics one of the hardAnthribidæ of the genus Ptychoderes, having long slender antennæ. In theMoluccas we find Cacia anthriboides, a small Longicorn which might beeasily mistaken for a very common species of Anthribidæ found in thesame districts; and the very rare Capnolymma stygium closely imitatesthe common Mecocerus gazella, which abounded where it was taken. Doliopscurculionoides and other allied Longicorns from the Philippine Islandsmost curiously resemble, both in form and colouring, the brilliantPachyrhynchi, --Curculionidæ, which are almost peculiar to that group ofislands. The remaining family of Coleoptera most frequently imitated isthe Cicindelidæ. The rare and curious Longicorn, Collyrodes lacordairei, has exactly the form and colouring of the genus Collyris, while anundescribed species of Heteromera is exactly like a Therates, and wastaken running on the trunks of trees, as is the habit of that group. There is one curious example of a Longicorn mimicking a Longicorn, likethe Papilios and Heliconidæ which mimic their own allies. Agniafasciata, belonging to the sub-family Hypselominæ, and Nemophas grayi, belonging to the Lamiinæ, were taken in Amboyna on the same fallen treeat the same time, and were supposed to be the same species till theywere more carefully examined, and found to be structurally quitedifferent. The colouring of these insects is very remarkable, being richsteel-blue black, crossed by broad hairy bands of orange buff, and outof the many thousands of known species of Longicorns they are probablythe only two which are so coloured. The Nemophas grayi is the larger, stronger, and better armed insect, and belongs to a more widely spreadand dominant group, very rich in species and individuals, and istherefore most probably the subject of mimicry by the other species. _Beetles mimicking other Insects. _ We will now adduce a few cases in which beetles imitate other insects, and insects of other orders imitate beetles. Charis melipona, a South American Longicorn of the family Necydalidæ, has been so named from its resemblance to a small bee of the genusMelipona. It is one of the most remarkable cases of mimicry, since thebeetle has the thorax and body densely hairy like the bee, and the legsare tufted in a manner most unusual in the order Coleoptera. AnotherLongicorn, Odontocera odyneroides, has the abdomen banded with yellow, and constricted at the base, and is altogether so exactly like a smallcommon wasp of the genus Odynerus, that Mr. Bates informs us he wasafraid to take it out of his net with his fingers for fear of beingstung. Had Mr. Bates's taste for insects been less omnivorous than itwas, the beetle's disguise might have saved it from his pin, as it hadno doubt often done from the beak of hungry birds. A larger insect, Sphecomorpha chalybea, is exactly like one of the large metallic bluewasps, and like them has the abdomen connected with the thorax by apedicel, rendering the deception most complete and striking. ManyEastern species of Longicorns of the genus Oberea, when on the wingexactly resemble Tenthredinidæ, and many of the small species ofHesthesis run about on timber, and cannot be distinguished from ants. There is one genus of South American Longicorns that appears to mimicthe shielded bugs of the genus Scutellera. The Gymnocerous capucinus isone of these, and is very like Pachyotris fabricii, one of theScutelleridæ. The beautiful Gymnocerous dulcissimus is also very likethe same group of insects, though there is no known species that exactlycorresponds to it; but this is not to be wondered at, as the tropicalHemiptera have been comparatively so little cared for by collectors. _Insects mimicking Species of other Orders. _ The most remarkable case of an insect of another order mimicking abeetle is that of the Condylodera tricondyloides, one of the cricketfamily from the Philippine Islands, which is so exactly like aTricondyla (one of the tiger beetles), that such an experiencedentomologist as Professor Westwood placed it among them in his cabinet, and retained it there a long time before he discovered his mistake! Bothinsects run along the trunks of trees, and whereas Tricondylas are veryplentiful, the insect that mimics it is, as in all other cases, veryrare. Mr. Bates also informs us that he found at Santarem on the Amazon, a species of locust which mimicked one of the tiger beetles of the genusOdontocheila, and was found on the same trees which they frequented. There are a considerable number of Diptera, or two-winged flies, thatclosely resemble wasps and bees, and no doubt derive much benefit fromthe wholesome dread which those insects excite. The Midas dives, andother species of large Brazilian flies, have dark wings and metallicblue elongate bodies, resembling the large stinging Sphegidæ of the samecountry; and a very large fly of the genus Asilus has black-bandedwings and the abdomen tipped with rich orange, so as exactly to resemblethe fine bee Euglossa dimidiata, and both are found in the same parts ofSouth America. We have also in our own country species of Bombyliuswhich are almost exactly like bees. In these cases the end gained by themimicry is no doubt freedom from attack, but it has sometimes analtogether different purpose. There are a number of parasitic flieswhose larvæ feed upon the larvæ of bees, such as the British genusVolucella and many of the tropical Bombylii, and most of these areexactly like the particular species of bee they prey upon, so that theycan enter their nests unsuspected to deposit their eggs. There are alsobees that mimic bees. The cuckoo bees of the genus Nomada are parasiticon the Andrenidæ, and they resemble either wasps or species of Andrena;and the parasitic humble-bees of the genus Apathus almost exactlyresemble the species of humble-bees in whose nests they are reared. Mr. Bates informs us that he found numbers of these "cuckoo" bees and flieson the Amazon, which all wore the livery of working bees peculiar to thesame country. There is a genus of small spiders in the tropics which feed on ants, andthey are exactly like ants themselves, which no doubt gives them moreopportunity of seizing their prey; and Mr. Bates found on the Amazon aspecies of Mantis which exactly resembled the white ants which it fedupon, as well as several species of crickets (Scaphura), which resembledin a wonderful manner different sand-wasps of large size, which areconstantly on the search for crickets with which to provision theirnests. Perhaps the most wonderful case of all is the large caterpillarmentioned by Mr. Bates, which startled him by its close resemblance to asmall snake. The first three segments behind the head were dilatable atthe will of the insect, and had on each side a large black pupillatedspot, which resembled the eye of the reptile. Moreover, it resembled apoisonous viper, not a harmless species of snake, as was proved by theimitation of keeled scales on the crown produced by the recumbent feet, as the caterpillar threw itself backward! The attitudes of many of the tropical spiders are most extraordinary anddeceptive, but little attention has been paid to them. They often mimicother insects, and some, Mr. Bates assures us, are exactly like flowerbuds, and take their station in the axils of leaves, where they remainmotionless waiting for their prey. _Cases of Mimicry among the Vertebrata. _ Having thus shown how varied and extraordinary are the modes in whichmimicry occurs among insects, we have now to enquire if anything of thesame kind is to be observed among vertebrated animals. When we considerall the conditions necessary to produce a good deceptive imitation, weshall see at once that such can very rarely occur in the higher animals, since they possess none of those facilities for the almost infinitemodifications of external form which exist in the very nature of insectorganization. The outer covering of insects being more or less solidand horny, they are capable of almost any amount of change of form andappearance without any essential modification internally. In many groupsthe wings give much of the character, and these organs may be muchmodified both in form and colour without interfering with their specialfunctions. Again, the number of species of insects is so great, andthere is such diversity of form and proportion in every group, that thechances of an accidental approximation in size, form, and colour, of oneinsect to another of a different group, are very considerable; and it isthese chance approximations that furnish the basis of mimicry, to becontinually advanced and perfected by the survival of those varietiesonly which tend in the right direction. In the Vertebrata, on the contrary, the skeleton being internal theexternal form depends almost entirely on the proportions and arrangementof that skeleton, which again is strictly adapted to the functionsnecessary for the well-being of the animal. The form cannot therefore berapidly modified by variation, and the thin and flexible integument willnot admit of the development of such strange protuberances as occurcontinually in insects. The number of species of each group in the samecountry is also comparatively small, and thus the chances of that firstaccidental resemblance which is necessary for natural selection to workupon are much diminished. We can hardly see the possibility of a mimicryby which the elk could escape from the wolf, or the buffalo from thetiger. There is, however, in one group of Vertebrata such a generalsimilarity of form, that a very slight modification, if accompanied byidentity of colour, would produce the necessary amount of resemblance;and at the same time there exist a number of species which it would beadvantageous for others to resemble, since they are armed with the mostfatal weapons of offence. We accordingly find that reptiles furnish uswith a very remarkable and instructive case of true mimicry. _Mimicry among Snakes. _ There are in tropical America a number of venomous snakes of the genusElaps, which are ornamented with brilliant colours disposed in apeculiar manner. The ground colour is generally bright red, on which areblack bands of various widths and sometimes divided into two or three byyellow rings. Now, in the same country are found several genera ofharmless snakes, having no affinity whatever with the above, butcoloured exactly the same. For example, the poisonous Elaps fulviusoften occurs in Guatemala with simple black bands on a coral-red ground;and in the same country is found the harmless snake Pliocerus equalis, coloured and banded in identically the same manner. A variety of Elapscorallinus has the black bands narrowly bordered with yellow on the samered ground colour, and a harmless snake, Homalocranium semicinctum, hasexactly the same markings, and both are found in Mexico. The deadlyElaps lemniscatus has the black bands very broad, and each of themdivided into three by narrow yellow rings; and this again is exactlycopied by a harmless snake, Pliocerus elapoides, which is found alongwith its model in Mexico. But, more remarkable still, there is in South America a third group ofsnakes, the genus Oxyrhopus, doubtfully venomous, and having noimmediate affinity with either of the preceding, which has also the samecurious distribution of colours, namely, variously disposed rings ofred, yellow, and black; and there are some cases in which species of allthree of these groups similarly marked inhabit the same district. Forexample, Elaps mipartitus has single black rings very close together. Itinhabits the west side of the Andes, and in the same districts occurPliocerus euryzonus and Oxyrhopus petolarius, which exactly copy itspattern. In Brazil Elaps lemniscatus is copied by Oxyrhopus trigeminus, both having black rings disposed in threes. In Elaps hemiprichii theground colour appears to be black, with alternations of two narrowyellow bands and a broader red one; and of this pattern again we have anexact double in Oxyrhopus formosus, both being found in many localitiesof tropical South America. What adds much to the extraordinary character of these resemblances isthe fact, that nowhere in the world but in America are there any snakesat all which have this style of colouring. Dr. Gunther, of the BritishMuseum, who has kindly furnished some of the details here referred to, assures me that this is the case; and that red, black, and yellow ringsoccur together on no other snakes in the world but on Elaps and thespecies which so closely resemble it. In all these cases, the size andform as well as the colouration, are so much alike, that none but anaturalist would distinguish the harmless from the poisonous species. Many of the small tree-frogs are no doubt also mimickers. When seen intheir natural attitudes, I have been often unable to distinguish themfrom beetles or other insects sitting upon leaves, but regret to say Ineglected to observe what species or groups they most resembled, and thesubject does not yet seem to have attracted the attention of naturalistsabroad. _Mimicry among Birds. _ In the class of birds there are a number of cases that make someapproach to mimicry, such as the resemblance of the cuckoos, a weak anddefenceless group of birds, to hawks and Gallinaceæ. There is, however, one example which goes much further than this, and seems to be ofexactly the same nature as the many cases of insect mimicry which havebeen already given. In Australia and the Moluccas there is a genus ofhoneysuckers called Tropidorhynchus, good sized birds, very strong andactive, having powerful grasping claws and long, curved, sharp beaks. They assemble together in groups and small flocks, and they have a veryloud bawling note, which can be heard at a great distance, and serves tocollect a number together in time of danger. They are very plentifuland very pugnacious, frequently driving away crows, and even hawks, which perch on a tree where a few of them are assembled. They are all ofrather dull and obscure colours. Now in the same countries there is agroup of orioles, forming the genus Mimeta, much weaker birds, whichhave lost the gay colouring of their allies the golden orioles, beingusually olive-green or brown; and in several cases these most curiouslyresemble the Tropidorhynchus of the same island. For example, in theisland of Bouru is found the Tropidorhynchus bouruensis, of a dullearthy colour, and the Mimeta bouruensis, which resembles it in thefollowing particulars:--The upper and under surfaces of the two birdsare exactly of the same tints of dark and light brown; theTropidorhynchus has a large bare black patch round the eyes; this iscopied in the Mimeta by a patch of black feathers. The top of the headof the Tropidorhynchus has a scaly appearance from the narrowscale-formed feathers, which are imitated by the broader feathers of theMimeta having a dusky line down each. The Tropidorhynchus has a paleruff formed of curious recurved feathers on the nape (which has giventhe whole genus the name of Friar birds); this is represented in theMimeta by a pale band in the same position. Lastly, the bill of theTropidorhynchus is raised into a protuberant keel at the base, and theMimeta has the same character, although it is not a common one in thegenus. The result is, that on a superficial examination the birds areidentical, although they have important structural differences, andcannot be placed near each other in any natural arrangement. As a proofthat the resemblance is really deceptive, it may be mentioned that theMimeta is figured and described as a honeysucker in the costly "Voyagede l'Astrolabe, " under the name of Philedon bouruensis! Passing to the island of Ceram, we find allied species of both genera. The Tropidorhynchus subcornutus is of an earthy brown colour washed withyellow ochre, with bare orbits, dusky cheeks, and the usual palerecurved nape-ruff. The Mimeta forsteni is absolutely identical in thetints of every part of the body, the details of which are imitated inthe same manner as in the Bouru birds already described. In two otherislands there is an approximation towards mimicry, although it is not soperfect as in the two preceding cases. In Timor the Tropidorhynchustimoriensis is of the usual earthy brown above, with the nape-ruff veryprominent, the cheeks black, the throat nearly white, and the wholeunder surface pale whitish brown. These various tints are all wellreproduced in Mimeta virescens, the chief want of exact imitation beingthat the throat and breast of the Tropidorhynchus has a very scalyappearance, being covered with rigid pointed feathers which are notimitated in the Mimeta, although there are signs of faint dusky spotswhich may easily furnish the groundwork of a more exact imitation by thecontinued survival of favourable variations in the same direction. Thereis also a large knob at the base of the bill of the Tropidorhynchuswhich is not at all imitated by the Mimeta. In the island of Morty(north of Gilolo) there exists the Tropidorhynchus fuscicapillus, of adark sooty brown colour, especially on the head, while the under partsare rather lighter, and the characteristic ruff of the nape is wanting. Now it is curious that in the adjacent island of Gilolo should be foundthe Mimeta phæochromus, the upper surface of which is of exactly thesame dark sooty tint as the Tropidorhynchus, and is the only knownspecies that is of such a dark colour. The under side is not quite lightenough, but it is a good approximation. This Mimeta is a rare bird, andmay very probably exist in Morty, though not yet found there; or, on theother hand, recent changes in physical geography may have led to therestriction of the Tropidorhynchus to that island, where it is verycommon. Here, then, we have two cases of perfect mimicry and two others of goodapproximation, occurring between species of the same two genera ofbirds; and in three of these cases the pairs that resemble each otherare found together in the same island, and to which they are peculiar. In all these cases the Tropidorhynchus is rather larger than the Mimeta, but the difference is not beyond the limits of variation in species, andthe two genera are somewhat alike in form and proportion. There are, nodoubt, some special enemies by which many small birds are attacked, butwhich are afraid of the Tropidorhynchus (probably some of the hawks), and thus it becomes advantageous for the weak Mimeta to resemble thestrong, pugnacious, noisy, and very abundant Tropidorhynchus. My friend, Mr. Osbert Salvin, has given me another interesting case ofbird mimicry. In the neighbourhood of Rio Janeiro is found aninsect-eating hawk (Harpagus diodon), and in the same district abird-eating hawk (Accipiter pileatus) which closely resembles it. Bothare of the same ashy tint beneath, with the thighs and underwing-coverts reddish brown, so that when on the wing and seen from belowthey are undistinguishable. The curious point, however, is that theAccipiter has a much wider range than the Harpagus, and in the regionswhere the insect-eating species is not found it no longer resembles it, the under wing-coverts varying to white; thus indicating that thered-brown colour is kept true by its being useful to the Accipiter to bemistaken for the insect-eating species, which birds have learnt not tobe afraid of. _Mimicry among Mammals. _ Among the Mammalia the only case which may be true mimicry is that ofthe insectivorous genus Cladobates, found in the Malay countries, several species of which very closely resemble squirrels. The size isabout the same, the long bushy tail is carried in the same way, and thecolours are very similar. In this case the use of the resemblance mustbe to enable the Cladobates to approach the insects or small birds onwhich it feeds, under the disguise of the harmless fruit-eatingsquirrel. _Objections to Mr. Bates' Theory of Mimicry. _ Having now completed our survey of the most prominent and remarkablecases of mimicry that have yet been noticed, we must say something ofthe objections that have been made to the theory of their productiongiven by Mr. Bates, and which we have endeavoured to illustrate andenforce in the preceding pages. Three counter explanations have beenproposed. Professor Westwood admits the fact of the mimicry and itsprobable use to the insect, but maintains that each species was createda mimic for the purpose of the protection thus afforded it. Mr. AndrewMurray, in his paper on the "Disguises of Nature, " inclines to theopinion that similar conditions of food and of surrounding circumstanceshave acted in some unknown way to produce the resemblances; and when thesubject was discussed before the Entomological Society of London, athird objection was added--that heredity or the reversion to ancestraltypes of form and colouration, might have produced many of the cases ofmimicry. Against the special creation of mimicking species there are all theobjections and difficulties in the way of special creation in othercases, with the addition of a few that are peculiar to it. The mostobvious is, that we have gradations of mimicry and of protectiveresemblance--a fact which is strongly suggestive of a natural processhaving been at work. Another very serious objection is, that as mimicryhas been shown to be useful only to those species and groups which arerare and probably dying out, and would cease to have any effect shouldthe proportionate abundance of the two species be reversed, it followsthat on the special-creation theory the one species must have beencreated plentiful, the other rare; and, notwithstanding the many causesthat continually tend to alter the proportions of species, these twospecies must have always been specially maintained at their respectiveproportions, or the very purpose for which they each received theirpeculiar characteristics would have completely failed. A thirddifficulty is, that although it is very easy to understand how mimicrymay be brought about by variation and the survival of the fittest, itseems a very strange thing for a Creator to protect an animal by makingit imitate another, when the very assumption of a Creator implies hispower to create it so as to require no such circuitous protection. Theseappear to be fatal objections to the application of the special-creationtheory to this particular case. The other two supposed explanations, which may be shortly expressed asthe theories of "similar conditions" and of "heredity, " agree in makingmimicry, where it exists, an adventitious circumstance not necessarilyconnected with the well-being of the mimicking species. But several ofthe most striking and most constant facts which have been adduced, directly contradict both those hypotheses. The law that mimicry isconfined to a few groups only is one of these, for "similar conditions"must act more or less on all groups in a limited region, and "heredity"must influence all groups related to each other in an equal degree. Again, the general fact that those species which mimic others are rare, while those which are imitated are abundant, is in no way explained byeither of these theories, any more than is the frequent occurrence ofsome palpable mode of protection in the imitated species. "Reversion toan ancestral type" no way explains why the imitator and the imitatedalways inhabit the very same district, whereas allied forms of everydegree of nearness and remoteness generally inhabit different countries, and often different quarters of the globe; and neither it, nor "similarconditions, " will account for the likeness between species of distinctgroups being superficial only--a disguise, not a true resemblance; forthe imitation of bark, of leaves, of sticks, of dung; for theresemblance between species in different orders, and even differentclasses and sub-kingdoms; and finally, for the graduated series of thephenomena, beginning with a general harmony and adaptation of tint inautumn and winter moths and in arctic and desert animals, and endingwith those complete cases of detailed mimicry which not only deceivepredacious animals, but puzzle the most experienced insect collectorsand the most learned entomologists. _Mimicry by Female Insects only. _ But there is yet another series of phenomena connected with thissubject, which considerably strengthens the view here adopted, while itseems quite incompatible with either of the other hypotheses; namely, the relation of protective colouring and mimicry to the sexualdifferences of animals. It will be clear to every one that if twoanimals, which as regards "external conditions" and "hereditarydescent, " are exactly alike, yet differ remarkably in colouration, oneresembling a protected species and the other not, the resemblance thatexists in one only can hardly be imputed to the influence of externalconditions or as the effect of heredity. And if, further, it can beproved that the one requires protection more than the other, and that inseveral cases it is that one which mimics the protected species, whilethe one that least requires protection never does so, it will affordvery strong corroborative evidence that there is a real connexionbetween the necessity for protection and the phenomenon of mimicry. Nowthe sexes of insects offer us a test of the nature here indicated, andappear to furnish one of the most conclusive arguments in favour of thetheory that the phenomena termed "mimicry" are produced by naturalselection. The comparative importance of the sexes varies much in different classesof animals. In the higher vertebrates, where the number of youngproduced at a birth is small and the same individuals breed many yearsin succession, the preservation of both sexes is almost equallyimportant. In all the numerous cases in which the male protects thefemale and her offspring, or helps to supply them with food, hisimportance in the economy of nature is proportionately increased, though it is never perhaps quite equal to that of the female. Ininsects the case is very different; they pair but once in their lives, and the prolonged existence of the male is in most cases quiteunnecessary for the continuance of the race. The female, however, mustcontinue to exist long enough to deposit her eggs in a place adapted forthe development and growth of the progeny. Hence there is a widedifference in the need for protection in the two sexes; and we should, therefore, expect to find that in some cases the special protectiongiven to the female was in the male less in amount or altogetherwanting. The facts entirely confirm this expectation. In the spectreinsects (Phasmidæ) it is often the females alone that so strikinglyresemble leaves, while the males show only a rude approximation. Themale Diadema misippus is a very handsome and conspicuous butterfly, without a sign of protective or imitative colouring, while the female isentirely unlike her partner, and is one of the most wonderful cases ofmimicry on record, resembling most accurately the common Danaischrysippus, in whose company it is often found. So in several species ofSouth American Pieris, the males are white and black, of a similar typeof colouring to our own "cabbage" butterflies, while the females arerich yellow and buff, spotted and marked so as exactly to resemblespecies of Heliconidæ with which they associate in the forest. In theMalay archipelago is found a Diadema which had always been considered amale insect on account of its glossy metallic-blue tints, while itscompanion of sober brown was looked upon as the female. I discovered, however, that the reverse is the case, and that the rich and glossycolours of the female are imitative and protective, since they cause herexactly to resemble the common Euploea midamus of the same regions, aspecies which has been already mentioned in this essay as mimicked byanother butterfly, Papilio paradoxa. I have since named this interestingspecies Diadema anomala (see the Transactions of the EntomologicalSociety, 1869, p. 285). In this case, and in that of Diadema misippus, there is no difference in the habits of the two sexes, which fly insimilar localities; so that the influence of "external conditions"cannot be invoked here as it has been in the case of the South AmericanPieris pyrrha and allies, where the white males frequent open sunnyplaces, while the Heliconia-like females haunt the shades of the forest. We may impute to the same general cause (the greater need of protectionfor the female, owing to her weaker flight, greater exposure to attack, and supreme importance)--the fact of the colours of female insects beingso very generally duller and less conspicuous than those of the othersex. And that it is chiefly due to this cause rather than to what Mr. Darwin terms "sexual selection" appears to be shown by the otherwiseinexplicable fact, that in the groups which have a protection of anykind independent of concealment, sexual differences of colour are eitherquite wanting or slightly developed. The Heliconidæ and Danaidæ, protected by a disagreeable flavour, have the females as bright andconspicuous as the males, and very rarely differing at all from them. The stinging Hymenoptera have the two sexes equally well coloured. TheCarabidæ, the Coccinellidæ, Chrysomelidæ, and the Telephori have bothsexes equally conspicuous, and seldom differing in colours. Thebrilliant Curculios, which are protected by their hardness, arebrilliant in both sexes. Lastly, the glittering Cetoniadæ andBuprestidæ, which seem to be protected by their hard and polished coats, their rapid motions, and peculiar habits, present few sexual differencesof colour, while sexual selection has often manifested itself bystructural differences, such as horns, spines, or other processes. _Cause of the dull Colours of Female Birds. _ The same law manifests itself in Birds. The female while sitting on hereggs requires protection by concealment to a much greater extent thanthe male; and we accordingly find that in a large majority of the casesin which the male birds are distinguished by unusual brilliancy ofplumage, the females are much more obscure, and often remarkablyplain-coloured. The exceptions are such as eminently to prove the rule, for in most cases we can see a very good reason for them. In particular, there are a few instances among wading and gallinaceous birds in whichthe female has decidedly more brilliant colours than the male; but it isa most curious and interesting fact that in most if not all these casesthe males sit upon the eggs; so that this exception to the usual rulealmost demonstrates that it is because the process of incubation is atonce very important and very dangerous, that the protection of obscurecolouring is developed. The most striking example is that of the grayphalarope (Phalaropus fulicarius). When in winter plumage, the sexes ofthis bird are alike in colouration, but in summer the female is much themost conspicuous, having a black head, dark wings, and reddish-brownback, while the male is nearly uniform brown, with dusky spots. Mr. Gould in his "Birds of Great Britain" figures the two sexes in bothwinter and summer plumage, and remarks on the strange peculiarity of theusual colours of the two sexes being reversed, and also on the stillmore curious fact that the "male alone sits on the eggs, " which aredeposited on the bare ground. In another British bird, the dotterell, the female is also larger and more brightly-coloured than the male; andit seems to be proved that the males assist in incubation even if theydo not perform it entirely, for Mr. Gould tells us, "that they have beenshot with the breast bare of feathers, caused by sitting on the eggs. "The small quail-like birds forming the genus Turnix have also generallylarge and bright-coloured females, and we are told by Mr. Jerdon in his"Birds of India" that "the natives report that during the breedingseason the females desert their eggs and associate in flocks while themales are employed in hatching the eggs. " It is also an ascertainedfact, that the females are more bold and pugnacious than the males. Afurther confirmation of this view is to be found in the fact (nothitherto noticed) that in a large majority of the cases in which brightcolours exist in both sexes incubation takes place in a dark hole or ina dome-shaped nest. Female kingfishers are often equally brilliant withthe male, and they build in holes in banks. Bee-eaters, trogons, motmots, and toucans, all build in holes, and in none is there anydifference in the sexes, although they are, without exception, showybirds. Parrots build in holes in trees, and in the majority of casesthey present no marked sexual difference tending to concealment of thefemale. Woodpeckers are in the same category, since though the sexesoften differ in colour, the female is not generally less conspicuousthan the male. Wagtails and titmice build concealed nests, and thefemales are nearly as gay as their mates. The female of the prettyAustralian bird Pardalotus punctatus, is very conspicuously spotted onthe upper surface, and it builds in a hole in the ground. Thegay-coloured hang-nests (Icterinæ) and the equally brilliant tanagersmay be well contrasted; for the former, concealed in their coverednests, present little or no sexual difference of colour--while theopen-nested tanagers have the females dull-coloured and sometimes withalmost protective tints. No doubt there are many individual exceptionsto the rule here indicated, because many and various causes havecombined to determine both the colouration and the habits of birds. These have no doubt acted and re-acted on each other; and whenconditions have changed one of these characters may often have becomemodified, while the other, though useless, may continue by hereditarydescent an apparent exception to what otherwise seems a very generalrule. The facts presented by the sexual differences of colour in birdsand their mode of nesting, are on the whole in perfect harmony with thatlaw of protective adaptation of colour and form, which appears to havechecked to some extent the powerful action of sexual selection, and tohave materially influenced the colouring of female birds, as it hasundoubtedly done that of female insects. _Use of the gaudy Colours of many Caterpillars. _ Since this essay was first published a very curious difficulty has beencleared up by the application of the general principle of protectivecolouring. Great numbers of caterpillars are so brilliantly marked andcoloured as to be very conspicuous even at a considerable distance, andit has been noticed that such caterpillars seldom hide themselves. Otherspecies, however, are green or brown, closely resembling the colours ofthe substances on which they feed, while others again imitate sticks, and stretch themselves out motionless from a twig so as to look like oneof its branches. Now, as caterpillars form so large a part of the foodof birds, it was not easy to understand why any of them should have suchbright colours and markings as to make them specially visible. Mr. Darwin had put the case to me as a difficulty from another point ofview, for he had arrived at the conclusion that brilliant colouration inthe animal kingdom is mainly due to sexual selection, and this could nothave acted in the case of sexless larvæ. Applying here the analogy ofother insects, I reasoned, that since some caterpillars were evidentlyprotected by their imitative colouring, and others by their spiny orhairy bodies, the bright colours of the rest must also be in some wayuseful to them. I further thought that as some butterflies and mothswere greedily eaten by birds while others were distasteful to them, andthese latter were mostly of conspicuous colours, so probably thesebrilliantly coloured caterpillars were distasteful, and therefore nevereaten by birds. Distastefulness alone would however be of little serviceto caterpillars, because their soft and juicy bodies are so delicate, that if seized and afterwards rejected by a bird they would almostcertainly be killed. Some constant and easily perceived signal wastherefore necessary to serve as a warning to birds never to touch theseuneatable kinds, and a very gaudy and conspicuous colouring with thehabit of fully exposing themselves to view becomes such a signal, beingin strong contrast with the green or brown tints and retiring habits ofthe eatable kinds. The subject was brought by me before theEntomological Society (see Proceedings, March 4th, 1867), in order thatthose members having opportunities for making observations might do soin the following summer; and I also wrote a letter to the _Field_newspaper, begging that some of its readers would co-operate in makingobservations on what insects were rejected by birds, at the same timefully explaining the great interest and scientific importance of theproblem. It is a curious example of how few of the country readers ofthat paper are at all interested in questions of simple natural history, that I only obtained one answer from a gentleman in Cumberland, who gaveme some interesting observations on the general dislike and abhorrenceof all birds to the "Gooseberry Caterpillar, " probably that of theMagpie-moth (Abraxas grossulariata). Neither young pheasants, partridges, nor wild-ducks could be induced to eat it, sparrows andfinches never touched it, and all birds to whom he offered it rejectedit with evident dread and abhorrence. It will be seen that theseobservations are confirmed by those of two members of the EntomologicalSociety to whom we are indebted for more detailed information. In March, 1869, Mr. J. Jenner Weir communicated a valuable series ofobservations made during many years, but more especially in the twopreceding summers, in his aviary, containing the following birds of moreor less insectivorous habits:--Robin, Yellow-Hammer, Reed-bunting, Bullfinch, Chaffinch, Crossbill, Thrush, Tree-Pipit, Siskin, andRedpoll. He found that hairy caterpillars were uniformly rejected; fivedistinct species were quite unnoticed by all his birds, and were allowedto crawl about the aviary for days with impunity. The spiny caterpillarsof the Tortoiseshell and Peacock butterflies were equally rejected; butin both these cases Mr. Weir thinks it is the taste, not the hairs orspines, that are disagreeable, because some very young caterpillars of ahairy species were rejected although no hairs were developed, and thesmooth pupæ of the above-named butterflies were refused as persistentlyas the spined larvæ. In these cases, then, both hairs and spines wouldseem to be mere signs of uneatableness. His next experiments were with those smooth gaily-coloured caterpillarswhich never conceal themselves, but on the contrary appear to courtobservation. Such are those of the Magpie moth (Abraxas grossulariata), whose caterpillar is conspicuously white and black spotted--the Dilobacoeruleocephala, whose larvæ is pale yellow with a broad blue or greenlateral band--the Cucullia verbasci, whose larvæ is greenish white withyellow bands and black spots, and Anthrocera filipendulæ (the six spotBurnet moth), whose caterpillar is yellow with black spots. These weregiven to the birds at various times, sometimes mixed with other kinds oflarvæ which were greedily eaten, but they were in every case rejectedapparently unnoticed, and were left to crawl about till they died. The next set of observations were on the dull-coloured and protectedlarvæ, and the results of numerous experiments are thus summarised byMr. Weir. "All caterpillars whose habits are nocturnal, which are dullcoloured, with fleshy bodies and smooth skins, are eaten with thegreatest avidity. Every species of green caterpillar is also muchrelished. All Geometræ, whose larvæ resemble twigs as they stand outfrom the plant on their anal prolegs, are invariably eaten. " At the same meeting Mr. A. G. Butler, of the British Museum, communicated the results of his observations with lizards, frogs, andspiders, which strikingly corroborate those of Mr. Weir. Three greenlizards (Lacerta viridis) which he kept for several years, were veryvoracious, eating all kinds of food, from a lemon cheesecake to aspider, and devouring flies, caterpillars, and humble bees; yet therewere some caterpillars and moths which they would seize only to dropimmediately. Among these the principal were the caterpillar of theMagpie moth (Abraxas grossulariata) and the perfect six spot Burnet moth(Anthrocera filipendulæ). These would be first seized but invariablydropped in disgust, and afterwards left unmolested. Subsequently frogswere kept and fed with caterpillars from the garden, but two ofthese--that of the before-mentioned Magpie moth, and that of the V. Moth(Halia wavaria), which is green with conspicuous white or yellow stripesand black spots--were constantly rejected. When these species were firstoffered, the frogs sprang at them eagerly and licked them into theirmouths; no sooner, however, had they done so than they seemed to beaware of the mistake that they had made, and sat with gaping mouths, rolling their tongues about until they had got quit of the nauseousmorsels. With spiders the same thing occurred. These two caterpillars wererepeatedly put into the webs both of the geometrical and hunting spiders(Epeira diadema and Lycosa sp. ), but in the former case they were cutout and allowed to drop; in the latter, after disappearing in the jawsof their captor down his dark silken funnel, they invariably reappeared, either from below or else taking long strides up the funnel again. Mr. Butler has observed lizards fight with and finally devour humble bees, and a frog sitting on a bed of stone-crop leap up and catch the beeswhich flew over his head, and swallow them, in utter disregard of theirstings. It is evident, therefore, that the possession of a disagreeabletaste or odour is a more effectual protection to certain conspicuouscaterpillars and moths, than would be even the possession of a sting. The observations of these two gentlemen supply a very remarkableconfirmation of the hypothetical solution of the difficulty which I hadgiven two years before. And as it is generally acknowledged that thebest test of the truth and completeness of a theory is the power whichit gives us of prevision, we may I think fairly claim this as a case inwhich the power of prevision has been successfully exerted, andtherefore as furnishing a very powerful argument in favour of the truthof the theory of Natural Selection. _Summary. _ I have now completed a brief, and necessarily very imperfect, survey ofthe various ways in which the external form and colouring of animals isadapted to be useful to them, either by concealing them from theirenemies or from the creatures they prey upon. It has, I hope, been shownthat the subject is one of much interest, both as regard a truecomprehension of the place each animal fills in the economy of nature, and the means by which it is enabled to maintain that place; and also asteaching us how important a part is played by the minutest details inthe structure of animals, and how complicated and delicate is theequilibrium of the organic world. My exposition of the subject having been necessarily somewhat lengthyand full of details, it will be as well to recapitulate its main points. There is a general harmony in nature between the colours of an animaland those of its habitation. Arctic animals are white, desert animalsare sand-coloured; dwellers among leaves and grass are green; nocturnalanimals are dusky. These colours are not universal, but are verygeneral, and are seldom reversed. Going on a little further, we findbirds, reptiles, and insects, so tinted and mottled as exactly to matchthe rock, or bark, or leaf, or flower, they are accustomed to restupon, --and thereby effectually concealed. Another step in advance, andwe have insects which are formed as well as coloured so as exactly toresemble particular leaves, or sticks, or mossy twigs, or flowers; andin these cases very peculiar habits and instincts come into play to aidin the deception and render the concealment more complete. We now enterupon a new phase of the phenomena, and come to creatures whose coloursneither conceal them nor make them like vegetable or mineral substances;on the contrary, they are conspicuous enough, but they completelyresemble some other creature of a quite different group, while theydiffer much in outward appearance from those with which all essentialparts of their organization show them to be really closely allied. Theyappear like actors or masqueraders dressed up and painted for amusement, or like swindlers endeavouring to pass themselves off for well-known andrespectable members of society. What is the meaning of this strangetravestie? Does Nature descend to imposture or masquerade? We answer, she does not. Her principles are too severe. There is a use in everydetail of her handiwork. The resemblance of one animal to another is ofexactly the same essential nature as the resemblance to a leaf, or tobark, or to desert sand, and answers exactly the same purpose. In theone case the enemy will not attack the leaf or the bark, and so thedisguise is a safeguard; in the other case it is found that for variousreasons the creature resembled is passed over, and not attacked by theusual enemies of its order, and thus the creature that resembles it hasan equally effectual safeguard. We are plainly shown that the disguiseis of the same nature in the two cases, by the occurrence in the samegroup of one species resembling a vegetable substance, while anotherresembles a living animal of another group; and we know that thecreatures resembled, possess an immunity from attack, by their beingalways very abundant, by their being conspicuous and not concealingthemselves, and by their having generally no visible means of escapefrom their enemies; while, at the same time, the particular quality thatmakes them disliked is often very clear, such as a nasty taste or anindigestible hardness. Further examination reveals the fact that, inseveral cases of both kinds of disguise, it is the female only that isthus disguised; and as it can be shown that the female needs protectionmuch more than the male, and that her preservation for a much longerperiod is absolutely necessary for the continuance of the race, we havean additional indication that the resemblance is in all casessubservient to a great purpose--the preservation of the species. In endeavouring to explain these phenomena as having been brought aboutby variation and natural selection, we start with the fact that whitevarieties frequently occur, and when protected from enemies show noincapacity for continued existence and increase. We know, further, thatvarieties of many other tints occasionally occur; and as "the survivalof the fittest" must inevitably weed out those whose colours areprejudicial and preserve those whose colours are a safeguard, we requireno other mode of accounting for the protective tints of arctic anddesert animals. But this being granted, there is such a perfectlycontinuous and graduated series of examples of every kind of protectiveimitation, up to the most wonderful cases of what is termed "mimicry, "that we can find no place at which to draw the line, and say, --so farvariation and natural selection will account for the phenomena, but forall the rest we require a more potent cause. The counter theories thathave been proposed, that of the "special creation" of each imitativeform, that of the action of "similar conditions of existence" for someof the cases, and of the laws of "hereditary descent and the reversionto ancestral forms" for others, --have all been shown to be beset withdifficulties, and the two latter to be directly contradicted by some ofthe most constant and most remarkable of the facts to be accounted for. _General deductions as to Colour in Nature. _ The important part that "protective resemblance" has played indetermining the colours and markings of many groups of animals, willenable us to understand the meaning of one of the most striking facts innature, the uniformity in the colours of the vegetable as compared withthe wonderful diversity of the animal world. There appears no goodreason why trees and shrubs should not have been adorned with as manyvaried hues and as strikingly designed patterns as birds andbutterflies, since the gay colours of flowers show that there is noincapacity in vegetable tissues to exhibit them. But even flowersthemselves present us with none of those wonderful designs, thosecomplicated arrangements of stripes and dots and patches of colour, that harmonious blending of hues in lines and bands and shaded spots, which are so general a feature in insects. It is the opinion of Mr. Darwin that we owe much of the beauty of flowers to the necessity ofattracting insects to aid in their fertilisation, and that much of thedevelopment of colour in the animal world is due to "sexual selection, "colour being universally attractive, and thus leading to its propagationand increase; but while fully admitting this, it will be evident fromthe facts and arguments here brought forward, that very much of the_variety_ both of colour and markings among animals is due to thesupreme importance of concealment, and thus the various tints ofminerals and vegetables have been directly reproduced in the animalkingdom, and again and again modified as more special protection becamenecessary. We shall thus have two causes for the development of colourin the animal world, and shall be better enabled to understand how, bytheir combined and separate action, the immense variety we now beholdhas been produced. Both causes, however, will come under the general lawof "Utility, " the advocacy of which, in its broadest sense, we owealmost entirely to Mr. Darwin. A more accurate knowledge of the variedphenomena connected with this subject may not improbably give us someinformation both as to the senses and the mental faculties of the loweranimals. For it is evident that if colours which please us also attractthem, and if the various disguises which have been here enumerated areequally deceptive to them as to ourselves, then both their powers ofvision and their faculties of perception and emotion, must beessentially of the same nature as our own--a fact of high philosophicalimportance in the study of our own nature and our true relations to thelower animals. _Conclusion. _ Although such a variety of interesting facts have been alreadyaccumulated, the subject we have been discussing is one of whichcomparatively little is really known. The natural history of the tropicshas never yet been studied on the spot with a full appreciation of "whatto observe" in this matter. The varied ways in which the colouring andform of animals serve for their protection, their strange disguises asvegetable or mineral substances, their wonderful mimicry of otherbeings, offer an almost unworked and inexhaustible field of discoveryfor the zoologist, and will assuredly throw much light on the laws andconditions which have resulted in the wonderful variety of colour, shade, and marking which constitutes one of the most pleasingcharacteristics of the animal world, but the immediate causes of whichit has hitherto been most difficult to explain. If I have succeeded in showing that in this wide and picturesque domainof nature, results which have hitherto been supposed to depend eitherupon those incalculable combinations of laws which we term chance orupon the direct volition of the Creator, are really due to the actionof comparatively well-known and simple causes, I shall have attained mypresent purpose, which has been to extend the interest so generally feltin the more striking facts of natural history to a large class ofcurious but much neglected details; and to further, in however slight adegree, our knowledge of the subjection of the phenomena of life to the"Reign of Law. " IV. THE MALAYAN PAPILIONIDÆ OR SWALLOW-TAILED BUTTERFLIES, AS ILLUSTRATIVEOF THE THEORY OF NATURAL SELECTION. _Special Value of the Diurnal Lepidoptera for enquiries of this nature. _ When the naturalist studies the habits, the structure, or the affinitiesof animals, it matters little to which group he especially devoteshimself; all alike offer him endless materials for observation andresearch. But, for the purpose of investigating the phenomena ofgeographical distribution and of local, sexual, or general variation, the several groups differ greatly in their value and importance. Somehave too limited a range, others are not sufficiently varied in specificforms, while, what is of most importance, many groups have not receivedthat amount of attention over the whole region they inhabit, which couldfurnish materials sufficiently approaching to completeness to enable usto arrive at any accurate conclusions as to the phenomena they presentas a whole. It is in those groups which are, and have long been, favourites with collectors, that the student of distribution andvariation will find his materials the most satisfactory, from theircomparative completeness. Pre-eminent among such groups are the diurnal Lepidoptera orButterflies, whose extreme beauty and endless diversity have led totheir having been assiduously collected in all parts of the world, andto the numerous species and varieties having been figured in a series ofmagnificent works, from those of Cramer, the contemporary of Linnæus, down to the inimitable productions of our own Hewitson. [G] But, besidestheir abundance, their universal distribution, and the great attentionthat has been paid to them, these insects have other qualities thatespecially adapt them to elucidate the branches of inquiry alreadyalluded to. These are, the immense development and peculiar structure ofthe wings, which not only vary in form more than those of any otherinsects, but offer on both surfaces an endless variety of pattern, colouring, and texture. The scales, with which they are more or lesscompletely covered, imitate the rich hues and delicate surfaces of satinor of velvet, glitter with metallic lustre, or glow with the changeabletints of the opal. This delicately painted surface acts as a register ofthe minutest differences of organization--a shade of colour, anadditional streak or spot, a slight modification of outline continuallyrecurring with the greatest regularity and fixity, while the body andall its other members exhibit no appreciable change. The wings ofButterflies, as Mr. Bates has well put it, "serve as a tablet on whichNature writes the story of the modifications of species;" they enable usto perceive changes that would otherwise be uncertain and difficult ofobservation, and exhibit to us on an enlarged scale the effects of theclimatal and other physical conditions which influence more or lessprofoundly the organization of every living thing. +--------------------------------------------------------------+ | [G] W. C. Hewitson, Esq. , of Oatlands, Walton-on-Thames, | | author of "Exotic Butterflies" and several other works, | | illustrated by exquisite coloured figures drawn by himself; | | and owner of the finest collection of Butterflies in the | | world. | +--------------------------------------------------------------+ A proof that this greater sensibility to modifying causes is notimaginary may, I think, be drawn from the consideration, that while theLepidoptera as a whole are of all insects the least essentially variedin form, structure, or habits, yet in the number of their specific formsthey are not much inferior to those orders which range over a much widerfield of nature, and exhibit more deeply seated structuralmodifications. The Lepidoptera are all vegetable-feeders in theirlarva-state, and suckers of juices or other liquids in their perfectform. In their most widely separated groups they differ but little froma common type, and offer comparatively unimportant modifications ofstructure or of habits. The Coleoptera, the Diptera, or the Hymenoptera, on the other hand, present far greater and more essential variations. Ineither of these orders we have both vegetable and animal-feeders, aquatic, and terrestrial, and parasitic groups. Whole families aredevoted to special departments in the economy of nature. Seeds, fruits, bones, carcases, excrement, bark, have each their special and dependentinsect tribes from among them; whereas the Lepidoptera are, with but fewexceptions, confined to the one function of devouring the foliage ofliving vegetation. We might therefore anticipate that theirspecies--population would be only equal to that of sections of the otherorders having a similar uniform mode of existence; and the fact thattheir numbers are at all comparable with those of entire orders, so muchmore varied in organization and habits, is, I think, a proof that theyare in general highly susceptible of specific modification. _Question of the rank of the Papilionidæ. _ The Papilionidæ are a family of diurnal Lepidoptera which have hitherto, by almost universal consent, held the first rank in the order; andthough this position has recently been denied them, I cannot altogetheracquiesce in the reasoning by which it has been proposed to degrade themto a lower rank. In Mr. Bates's most excellent paper on the Heliconidæ, (published in the Transactions of the Linnæan Society, vol. Xxiii. , p. 495) he claims for that family the highest position, chiefly because ofthe imperfect structure of the fore legs, which is there carried to anextreme degree of abortion, and thus removes them further than any otherfamily from the Hesperidæ and Heterocera, which all have perfect legs. Now it is a question whether any amount of difference which is exhibitedmerely in the imperfection or abortion of certain organs, can establishin the group exhibiting it a claim to a high grade of organization, still less can this be allowed when another group along with perfectionof structure in the same organs, exhibits modifications peculiar to it, together with the possession of an organ which in the remainder of theorder is altogether wanting. This is, however, the position of thePapilionidæ. The perfect insects possess two characters quite peculiarto them. Mr. Edward Doubleday, in his "Genera of Diurnal Lepidoptera, "says, "The Papilionidæ may be known by the apparently four-branchedmedian nervule and the spur on the anterior tibiæ, characters found inno other family. " The four-branched median nervule is a character soconstant, so peculiar, and so well marked, as to enable a person totell, at a glance at the wings only of a butterfly, whether it does ordoes not belong to this family; and I am not aware that any other groupof butterflies, at all comparable to this in extent and modifications ofform, possesses a character in its neuration to which the same degree ofcertainty can be attached. The spur on the anterior tibiæ is also foundin some of the Hesperidæ, and is therefore supposed to show a directaffinity between the two groups: but I do not imagine it cancounterbalance the differences in neuration and in every other part oftheir organization. The most characteristic feature of the Papilionidæ, however, and that on which I think insufficient stress has been laid, isundoubtedly the peculiar structure of the larvæ. These all possess anextraordinary organ situated on the neck, the well-known Y-shapedtentacle, which is entirely concealed in a state of repose, but which iscapable of being suddenly thrown out by the insect when alarmed. When weconsider this singular apparatus, which in some species is nearly halfan inch long, the arrangement of muscles for its protrusion andretraction, its perfect concealment during repose, its blood-red colour, and the suddenness with which it can be thrown out, we must, I think, beled to the conclusion that it serves as a protection to the larva, bystartling and frightening away some enemy when about to seize it, and isthus one of the causes which has led to the wide extension andmaintained the permanence of this now dominant group. Those who believethat such peculiar structures can only have arisen by very minutesuccessive variations, each one advantageous to its possessor, must see, in the possession of such an organ by one group, and its completeabsence in every other, a proof of a very ancient origin and of verylong-continued modification. And such a positive structural addition tothe organization of the family, subserving an important function, seemsto me alone sufficient to warrant us in considering the Papilionidæ asthe most highly developed portion of the whole order, and thus inretaining it in the position which the size, strength, beauty, andgeneral structure of the perfect insects have been generally thought todeserve. In Mr. Trimen's paper on "Mimetic Analogies among African Butterflies, "in the Transactions of the Linnæan Society, for 1868, he has arguedstrongly in favour of Mr. Bates' views as to the higher position of theDanaidæ and the lower grade of the Papilionidæ, and has adduced, amongother facts, the undoubted resemblance of the pupa of Parnassius, agenus of Papilionidæ, to that of some Hesperidæ and moths. I admit, therefore, that he has proved the Papilionidæ to have retained severalcharacters of the nocturnal Lepidoptera which the Danaidæ have lost, butI deny that they are therefore to be considered lower in the scale oforganization. Other characters may be pointed out which indicate thatthey are farther removed from the moths even than the Danaidæ. The clubof the antennæ is the most prominent and most constant feature by whichbutterflies may be distinguished from moths, and of all butterflies thePapilionidæ have the most beautiful and most perfectly developed clubbedantennæ. Again, butterflies and moths are broadly characterised by theirdiurnal and nocturnal habits respectively, and the Papilionidæ, withtheir close allies the Pieridæ, are the most pre-eminently diurnal ofbutterflies, most of them lovers of sunshine, and not presenting asingle crepuscular species. The great group of the Nymphalidæ, on theother hand (in which Mr. Bates includes the Danaidæ and Heliconidæ assub-families), contains an entire sub-family (Brassolidæ) and a numberof genera, such as Thaumantis, Zeuxidia, Pavonia, &c. , of crepuscularhabits, while a large proportion of the Satyridæ and many of theDanaidæ are shade-loving butterflies. This question, of what is to beconsidered the highest type of any group of organisms, is one of suchgeneral interest to naturalists that it will be well to consider it alittle further, by a comparison of the Lepidoptera with some groups ofthe higher animals. Mr. Trimen's argument, that the lepidopterous type, like that of birds, being pre-eminently aërial, "therefore a diminution of the ambulatoryorgans, instead of being a sign of inferiority, may very possiblyindicate a higher, because a more thoroughly aërial form, " is certainlyunsound, for it would imply that the most aërial of birds (the swift andthe frigate-birds, for example) are the highest in the scale ofbird-organization, and the more so on account of their feet being veryill adapted for walking. But no ornithologist has ever so classed them, and the claim to the highest rank among birds is only disputed betweenthree groups, all very far removed from these. They are--1st. TheFalcons, on account of their general perfection, their rapid flight, their piercing vision, their perfect feet armed with retractile claws, the beauty of their forms, and the ease and rapidity of their motions;2nd. The Parrots, whose feet, though ill-fitted for walking, are perfectas prehensile organs, and which possess large brains with greatintelligence, though but moderate powers of flight; and, 3rd. TheThrushes or Crows, as typical of the perching birds, on account of thewell-balanced development of their whole structure, in which no organor function has attained an undue prominence. Turning now to the Mammalia, it might be argued that as they arepre-eminently the terrestrial type of vertebrates, to walk and run wellis essential to the typical perfection of the group; but this would givethe superiority to the horse, the deer, or the hunting leopard, insteadof to the Quadrumana. We seem here to have quite a case in point, forone group of Quadrumana, the Lemurs, is undoubtedly nearer to the lowInsectivora and Marsupials than the Carnivora or the Ungulata, as shownamong other characters by the Opossums possessing a hand with perfectopposable thumb, closely resembling that of some of the Lemurs; and bythe curious Galeopithecus, which is sometimes classed as a Lemur, andsometimes with the Insectivora. Again, the implacental mammals, including the Ornithodelphia and the Marsupials, are admitted to belower than the placental series. But one of the distinguishingcharacters of the Marsupials is that the young are born blind andexceedingly imperfect, and it might therefore be argued that thoseorders in which the young are born most perfect are the highest, becausefarthest from the low Marsupial type. This would make the Ruminants andUngulata higher than the Quadrumana or the Carnivora. But the Mammaliaoffer a still more remarkable illustration of the fallacy of this modeof reasoning, for if there is one character more than another which isessential and distinctive of the class, it is that from which it derivesits name, the possession of mammary glands and the power of sucklingthe young. What more reasonable, apparently, than to argue that thegroup in which this important function is most developed, that in whichthe young are most dependent upon it, and for the longest period, mustbe the highest in the Mammalian scale of organization? Yet this group isthe Marsupial, in which the young commence suckling in a foetalcondition, and continue to do so till they are fully developed, and aretherefore for a long time absolutely dependent on this mode ofnourishment. These examples, I think, demonstrate that we cannot settle the rank of agroup by a consideration of the degree in which certain charactersresemble or differ from those in what is admitted to be a lower group;and they also show that the highest group of a class may be more closelyconnected to one of the lowest, than some other groups which havedeveloped laterally and diverged farther from the parent type, but whichyet, owing to want of balance or too great specialization in theirstructure, have never reached a high grade of organization. TheQuadrumana afford a very valuable illustration, because, owing to theirundoubted affinity with man, we feel certain that they are really higherthan any other order of Mammalia, while at the same time they are moredistinctly allied to the lowest groups than many others. The case of thePapilionidæ seems to me so exactly parallel to this, that, while I admitall the proofs of affinity with the undoubtedly lower groups ofHesperidæ and moths, I yet maintain that, owing to the complete andeven development of every part of their organization, these insects bestrepresent the highest perfection to which the butterfly type hasattained, and deserve to be placed at its head in every system ofclassification. _Distribution of the Papilionidæ. _ The Papilionidæ are pretty widely distributed over the earth, but areespecially abundant in the tropics, where they attain their maximum ofsize and beauty, and the greatest variety of form and colouring. SouthAmerica, North India, and the Malay Islands are the regions where thesefine insects occur in the greatest profusion, and where they actuallybecome a not unimportant feature in the scenery. In the Malay Islands inparticular, the giant Ornithopteræ may be frequently seen about theborders of the cultivated and forest districts, their large size, stately flight, and gorgeous colouring rendering them even moreconspicuous than the generality of birds. In the shady suburbs of thetown of Malacca two large and handsome Papilios (Memnon and Nephelus)are not uncommon, flapping with irregular flight along the roadways, or, in the early morning, expanding their wings to the invigorating rays ofthe sun. In Amboyna and other towns of the Moluccas, the magnificentDeiphobus and Severus, and occasionally even the azure-winged Ulysses, frequent similar situations, fluttering about the orange-trees andflower-beds, or sometimes even straying into the narrow bazaars orcovered markets of the city. In Java the golden-dusted Arjuna may oftenbe seen at damp places on the roadside in the mountain districts, incompany with Sarpedon, Bathycles, and Agamemnon, and less frequently thebeautiful swallow-tailed Antiphates. In the more luxuriant parts ofthese islands one can hardly take a morning's walk in the neighbourhoodof a town or village without seeing three or four species of Papilio, and often twice that number. No less than 130 species of the family arenow known to inhabit the Archipelago, and of these ninety-six werecollected by myself. Thirty species are found in Borneo, being thelargest number in any one island, twenty-three species having beenobtained by myself in the vicinity of Sarawak; Java has twenty-eightspecies; Celebes twenty-four, and the Peninsula of Malacca, twenty-sixspecies. Further east the numbers decrease; Batchian producingseventeen, and New Guinea only fifteen, though this number is certainlytoo small, owing to our present imperfect knowledge of that greatisland. _Definition of the word Species. _ In estimating these numbers I have had the usual difficulty toencounter, of determining what to consider species and what varieties. The Malayan region, consisting of a large number of islands of generallygreat antiquity, possesses, compared to its actual area, a great numberof distinct forms, often indeed distinguished by very slightcharacters, but in most cases so constant in large series of specimens, and so easily separable from each other, that I know not on whatprinciple we can refuse to give them the name and rank of species. Oneof the best and most orthodox definitions is that of Pritchard, thegreat ethnologist, who says, that "_separate origin and distinctness ofrace, evinced by a constant transmission of some characteristicpeculiarity of organization_, " constitutes a species. Now leaving outthe question of "origin, " which we cannot determine, and taking only theproof of separate origin, "_the constant transmission of somecharacteristic peculiarity of organization_, " we have a definition whichwill compel us to neglect altogether the _amount_ of difference betweenany two forms, and to consider only whether the differences that presentthemselves are _permanent_. The rule, therefore, I have endeavoured toadopt is, that when the difference between two forms inhabiting separateareas seems quite constant, when it can be defined in words, and when itis not confined to a single peculiarity only, I have considered suchforms to be species. When, however, the individuals of each localityvary among themselves, so as to cause the distinctions between the twoforms to become inconsiderable and indefinite, or where the differences, though constant, are confined to one particular only, such as size, tint, or a single point of difference in marking or in outline, I classone of the forms as a variety of the other. I find as a general rule that the constancy of species is in an inverseratio to their range. Those which are confined to one or two islands aregenerally very constant. When they extend to many islands, considerablevariability appears; and when they have an extensive range over a largepart of the Archipelago, the amount of unstable variation is very large. These facts are explicable on Mr. Darwin's principles. When a speciesexists over a wide area, it must have had, and probably still possesses, great powers of dispersion. Under the different conditions of existencein various portions of its area, different variations from the typewould be selected, and, were they completely isolated, would soon becomedistinctly modified forms; but this process is checked by the dispersivepowers of the whole species, which leads to the more or less frequentintermixture of the incipient varieties, which thus become irregular andunstable. Where, however, a species has a limited range, it indicatesless active powers of dispersion, and the process of modification underchanged conditions is less interfered with. The species will thereforeexist under one or more permanent forms according as portions of it havebeen isolated at a more or less remote period. _Laws and Modes of Variation. _ What is commonly called variation consists of several distinct phenomenawhich have been too often confounded. I shall proceed to consider theseunder the heads of--1st, simple variability; 2nd, polymorphism; 3rd, local forms; 4th, co-existing varieties; 5th, races or subspecies; and6th, true species. 1. _Simple variability. _--Under this head I include all those cases inwhich the specific form is to some extent unstable. Throughout the wholerange of the species, and even in the progeny of individuals, thereoccur continual and uncertain differences of form, analogous to thatvariability which is so characteristic of domestic breeds. It isimpossible usefully to define any of these forms, because there areindefinite gradations to each other form. Species which possess thesecharacteristics have always a wide range, and are more frequently theinhabitants of continents than of islands, though such cases are alwaysexceptional, it being far more common for specific forms to be fixedwithin very narrow limits of variation. The only good example of thiskind of variability which occurs among the Malayan Papilionidæ is inPapilio Severus, a species inhabiting all the islands of the Moluccasand New Guinea, and exhibiting in each of them a greater amount ofindividual difference than often serves to distinguish well-markedspecies. Almost equally remarkable are the variations exhibited in mostof the species of Ornithoptera, which I have found in some cases toextend even to the form of the wing and the arrangement of the nervures. Closely allied, however, to these variable species are others which, though differing slightly from them, are constant and confined tolimited areas. After satisfying oneself, by the examination of numerousspecimens captured in their native countries, that the one set ofindividuals are variable and the others are not, it becomes evident thatby classing all alike as varieties of one species we shall be obscuringan important fact in nature; and that the only way to exhibit that factin its true light is to treat the invariable local form as a distinctspecies, even though it does not offer better distinguishing charactersthan do the extreme forms of the variable species. Cases of this kindare the Ornithoptera Priamus, which is confined to the islands of Ceramand Amboyna, and is very constant in both sexes, while the alliedspecies inhabiting New Guinea and the Papuan Islands is exceedinglyvariable; and in the island of Celebes is a species closely allied tothe variable P. Severus, but which, being exceedingly constant, I havedescribed as a distinct species under the name of Papilio Pertinax. 2. _Polymorphism or dimorphism. _--By this term I understand theco-existence in the same locality of two or more distinct forms, notconnected by intermediate gradations, and all of which are occasionallyproduced from common parents. These distinct forms generally occur inthe female sex only, and their offspring, instead of being hybrids, orlike the two parents, appear to reproduce all the distinct forms invarying proportions. I believe it will be found that a considerablenumber of what have been classed as _varieties_ are really cases ofpolymorphism. Albinoism and melanism are of this character, as well asmost of those cases in which well-marked varieties occur in company withthe parent species, but without any intermediate forms. If thesedistinct forms breed independently, and are never reproduced from acommon parent, they must be considered as separate species, contactwithout intermixture being a good test of specific difference. On theother hand, intercrossing without producing an intermediate race is atest of dimorphism. I consider, therefore, that under any circumstancesthe term "variety" is wrongly applied to such cases. The Malayan Papilionidæ exhibit some very curious instances ofpolymorphism, some of which have been recorded as varieties, others asdistinct species; and they all occur in the female sex. Papilio Memnonis one of the most striking, as it exhibits the mixture of simplevariability, local and polymorphic forms, all hitherto classed under thecommon title of varieties. The polymorphism is strikingly exhibited bythe females, one set of which resemble the males in form, with avariable paler colouring; the others have a large spatulate tail to thehinder wings and a distinct style of colouring, which causes themclosely to resemble P. Coon, a species having the two sexes alike andinhabiting the same countries, but with which they have no directaffinity. The tailless females exhibit simple variability, scarcely twobeing found exactly alike even in the same locality. The males of theisland of Borneo exhibit constant differences of the under surface, andmay therefore be distinguished as a local form, while the continentalspecimens, as a whole, offer such large and constant differences fromthose of the islands, that I am inclined to separate them as a distinctspecies, to which the name P. Androgeus (Cramer) may be applied. Wehave here, therefore, distinct species, local forms, polymorphism, andsimple variability, which seem to me to be distinct phenomena, but whichhave been hitherto all classed together as varieties. I may mention thatthe fact of these distinct forms being one species is doubly proved. Themales, the tailed and tailless females, have all been bred from a singlegroup of the larvæ, by Messrs. Payen and Bocarmé, in Java, and I myselfcaptured, in Sumatra, a male P. Memnon, and a tailed female P. Achates, under circumstances which led me to class them as the same species. Papilio Pammon offers a somewhat similar case. The female was describedby Linnæus as P. Polytes, and was considered to be a distinct speciestill Westermann bred the two from the same larvæ (see Boisduval, "Species Général des Lépidoptères, " p. 272). They were therefore classedas sexes of one species by Mr. Edward Doubleday, in his "Genera ofDiurnal Lepidoptera, " in 1846. Later, female specimens were receivedfrom India closely resembling the male insect, and this was held tooverthrow the authority of M. Westermann's observation, and tore-establish P. Polytes as a distinct species; and as such itaccordingly appears in the British Museum List of Papilionidæ in 1856, and in the Catalogue of the East India Museum in 1857. This discrepancyis explained by the fact of P. Pammon having two females, one closelyresembling the male, while the other is totally different from it. Along familiarity with this insect (which replaced by local forms or byclosely allied species, occurs in every island of the Archipelago) hasconvinced me of the correctness of this statement; for in every placewhere a male allied to P. Pammon is found, a female resembling P. Polytes also occurs, and sometimes, though less frequently than on thecontinent, another female closely resembling the male: while not onlyhas no male specimen of P. Polytes yet been discovered, but the female(Polytes) has never yet been found in localities to which the male(Pammon) does not extend. In this case, as in the last, distinctspecies, local forms, and dimorphic specimens, have been confoundedunder the common appellation of varieties. But, besides the true P. Polytes, there are several allied forms offemales to be considered, namely, P. Theseus (Cramer), P. Molanides (DeHaan), P. Elyros (G. R. Gray), and P. Romulus (Linnæus). The dark femalefigured by Cramer as P. Theseus seems to be the common and perhaps theonly form in Sumatra, whereas in Java, Borneo, and Timor, along withmales quite identical with those of Sumatra, occur females of thePolytes form, although a single specimen of the true P. Theseus taken atLombock would seem to show that the two forms do occur together. In theallied species found in the Philippine Islands (P. Alphenor, Cramer = P. Ledebouria, Eschscholtz, the female of which is P. Elyros, G. R. Gray, )forms corresponding to these extremes occur, along with a number ofintermediate varieties, as shown by a fine series in the British Museum. We have here an indication of how dimorphism may be produced; for letthe extreme Philippine forms be better suited to their conditions ofexistence than the intermediate connecting links, and the latter willgradually die out, leaving two distinct forms of the same insect, eachadapted to some special conditions. As these conditions are sure to varyin different districts, it will often happen, as in Sumatra and Java, that the one form will predominate in the one island, the other in theadjacent one. In the island of Borneo there seems to be a third form;for P. Melanides (De Haan) evidently belongs to this group, and has allthe chief characteristics of P. Theseus, with a modified colouration ofthe hind wings. I now come to an insect which, if I am correct, offersone of the most interesting cases of variation yet adduced. PapilioRomulus, a butterfly found over a large part of India and Ceylon, andnot uncommon in collections, has always been considered a true andindependent species, and no suspicions have been expressed regarding it. But a male of this form does not, I believe, exist. I have examined thefine series in the British Museum, in the East India Company's Museum, in the Hope Museum at Oxford, in Mr. Hewitson's and several otherprivate collections, and can find nothing but females; and for thiscommon butterfly no male partner can be found except the equally commonP. Pammon, a species already provided with two wives, and yet to whom weshall be forced, I believe, to assign a third. On carefully examining P. Romulus, I find that in all essential characters--the form and textureof the wings, the length of the antennæ, the spotting of the head andthorax, and even the peculiar tints and shades with which it isornamented--it corresponds exactly with the other females of the Pammongroup; and though, from the peculiar marking of the fore wings, it hasat first sight a very different aspect, yet a closer examination showsthat every one of its markings could be produced by slight and almostimperceptible modifications of the various allied forms. I fullybelieve, therefore, that I shall be correct in placing P. Romulus as athird Indian form of the female P. Pammon, corresponding to P. Melanides, the third form of the Malayan P. Theseus. I may mention herethat the females of this group have a superficial resemblance to thePolydorus group of Papilios, as shown by P. Theseus having beenconsidered to be the female of P. Antiphus, and by P. Romulus beingarranged next to P. Hector. There is no close affinity between these twogroups of Papilio, and I am disposed to believe that we have here a caseof mimicry, brought about by the same causes which Mr. Bates has so wellexplained in his account of the Heliconidæ, and which has led to thesingular exuberance of polymorphic forms in this and allied groups ofthe genus Papilio. I shall have to devote a section of my essay to theconsideration of this subject. The third example of polymorphism I have to bring forward is PapilioOrmenus, which is closely allied to the well-known P. Erechtheus, ofAustralia. The most common form of the female also resembles that of P. Erechtheus; but a totally different-looking insect was found by myselfin the Aru Islands, and figured by Mr. Hewitson under the name of P. Onesimus, which subsequent observation has convinced me is a second formof the female of P. Ormenus. Comparison of this with Boisduval'sdescription of P. Amanga, a specimen of which from New Guinea is in theParis Museum, shows the latter to be a closely similar form; and twoother specimens were obtained by myself, one in the island of Goram andthe other in Waigiou, all evidently local modifications of the sameform. In each of these localities males and ordinary females of P. Ormenus were also found. So far there is no evidence that theselight-coloured insects are not females of a distinct species, the malesof which have not been discovered. But two facts have convinced me thisis not the case. At Dorey, in New Guinea, where males and ordinaryfemales closely allied to P. Ormenus occur (but which seem to me worthyof being separated as a distinct species), I found one of theselight-coloured females closely followed in her flight by three males, exactly in the same manner as occurs (and, I believe, occurs only) withthe sexes of the same species. After watching them a considerable time, I captured the whole of them, and became satisfied that I had discoveredthe true relations of this anomalous form. The next year I hadcorroborative proof of the correctness of this opinion by the discoveryin the island of Batchian of a new species allied to P. Ormenus, all thefemales of which, either seen or captured by me, were of one form, andmuch more closely resembling the abnormal light-coloured females of P. Ormenus and P. Pandion than the ordinary specimens of that sex. Everynaturalist will, I think, agree that this is strongly confirmative ofthe supposition that both forms of female are of one species; and whenwe consider, further, that in four separate islands, in each of which Iresided for several months, the two forms of female were obtained andonly one form of male ever seen, and that about the same time, M. Montrouzier in Woodlark Island, at the other extremity of New Guinea(where he resided several years, and must have obtained all the largeLepidoptera of the island), obtained females closely resembling mine, which, in despair at finding no appropriate partners for them, he mateswith a widely different species--it becomes, I think, sufficientlyevident this is another case of polymorphism of the same nature as thosealready pointed out in P. Pammon and P. Memnon. This species, however, is not only dimorphic, but trimorphic; for, in the island of Waigiou, Iobtained a third female quite distinct from either of the others, and insome degree intermediate between the ordinary female and the male. Thespecimen is particularly interesting to those who believe, with Mr. Darwin, that extreme difference of the sexes has been gradually producedby what he terms sexual selection, since it may be supposed to exhibitone of the intermediate steps in that process, which has beenaccidentally preserved in company with its more favoured rivals, thoughits extreme rarity (only one specimen having been seen to many hundredsof the other form) would indicate that it may soon become extinct. The only other case of polymorphism in the genus Papilio, at all equalin interest to those I have now brought forward, occurs in America; andwe have, fortunately, accurate information about it. Papilio Turnus iscommon over almost the whole of temperate North America; and the femaleresembles the male very closely. A totally different-looking insect bothin form and colour, Papilio Glaucus, inhabits the same region; andthough, down to the time when Boisduval published his "Species Général, "no connexion was supposed to exist between the two species, it is nowwell ascertained that P. Glaucus is a second female form of P. Turnus. In the "Proceedings of the Entomological Society of Philadelphia, " Jan. , 1863, Mr. Walsh gives a very interesting account of the distribution ofthis species. He tells us that in the New England States and in New Yorkall the females are yellow, while in Illinois and further south all areblack; in the intermediate region both black and yellow females occur invarying proportions. Lat. 37° is approximately the southern limit of theyellow form, and 42° the northern limit of the black form; and, torender the proof complete, both black and yellow insects have been bredfrom a single batch of eggs. He further states that, out of thousandsof specimens, he has never seen or heard of intermediate varietiesbetween these forms. In this interesting example we see the effects oflatitude in determining the proportions in which the individuals of eachform should exist. The conditions are _here_ favourable to the one form, _there_ to the other; but we are by no means to suppose that theseconditions consist in climate alone. It is highly probable that theexistence of enemies, and of competing forms of life, may be the maindetermining influences; and it is much to be wished that such acompetent observer as Mr. Walsh would endeavour to ascertain what arethe adverse causes which are most efficient in keeping down the numbersof each of these contrasted forms. Dimorphism of this kind in the animal kingdom does not seem to have anydirect relations to the reproductive powers, as Mr. Darwin has shown tobe the case in plants, nor does it appear to be very general. One othercase only is known to me in another family of my eastern Lepidoptera, the Pieridæ; and but few occur in the Lepidoptera of other countries. The spring and autumn broods of some European species differ veryremarkably; and this must be considered as a phenomenon of an analogousthough not of an identical nature, while the Araschnia prorsa, ofCentral Europe, is a striking example of this alternate or seasonaldimorphism. Among our nocturnal Lepidoptera, I am informed, manyanalogous cases occur; and as the whole history of many of these hasbeen investigated by breeding successive generations from the egg, it isto be hoped that some of our British Lepidopterists will give us aconnected account of all the abnormal phenomena which they present. Among the Coleoptera Mr. Pascoe has pointed out the existence of twoforms of the male sex in seven species of the two genera Xenocerus andMecocerus belonging to the family Anthribidæ, (Proc. Ent. Soc. Lond. , 1862); and no less than six European Water-beetles, of the genusDytiscus, have females of two forms, the most common having the elytradeeply sulcate, the rarer smooth as in the males. The three, andsometimes four or more, forms under which many Hymenopterous insects(especially Ants) occur, must be considered as a related phenomenon, though here each form is specialized to a distinct function in theeconomy of the species. Among the higher animals, albinoism and melanismmay, as I have already stated, be considered as analogous facts; and Imet with one case of a bird, a species of Lory (Eos fuscata), clearlyexisting under two differently coloured forms, since I obtained bothsexes of each from a single flock, while no intermediate specimens haveyet been found. The fact of the two sexes of one species differing very considerably isso common, that it attracted but little attention till Mr. Darwin showedhow it could in many cases be explained by the principle of sexualselection. For instance, in most polygamous animals the males fight forthe possession of the females, and the victors, always becoming theprogenitors of the succeeding generation, impress upon their maleoffspring their own superior size, strength, or unusually developedoffensive weapons. It is thus that we can account for the spurs and thesuperior strength and size of the males in Gallinaceous birds, and alsofor the large canine tusks in the males of fruit-eating Apes. So thesuperior beauty of plumage and special adornments of the males of somany birds can be explained by supposing (what there are many facts toprove) that the females prefer the most beautiful and perfect-plumagedmales, and that thus, slight accidental variations of form and colourhave been accumulated, till they have produced the wonderful train ofthe Peacock and the gorgeous plumage of the Bird of Paradise. Both thesecauses have no doubt acted partially in insects, so many speciespossessing horns and powerful jaws in the male sex only, and still morefrequently the males alone rejoicing in rich colours or sparklinglustre. But there is here another cause which has led to sexualdifferences, viz. , a special adaptation of the sexes to diverse habitsor modes of life. This is well seen in female Butterflies (which aregenerally weaker and of slower flight), often having colours betteradapted to concealment; and in certain South American species (Papiliotorquatus) the females, which inhabit the forests, resemble the Æneasgroup of Papilios which abound in similar localities, while the males, which frequent the sunny open river-banks, have a totally differentcolouration. In these cases, therefore, natural selection seems to haveacted independently of sexual selection; and all such cases may beconsidered as examples of the simplest dimorphism, since the offspringnever offer intermediate varieties between the parent forms. The phenomena of dimorphism and polymorphism may be well illustrated bysupposing that a blue-eyed, flaxen-haired Saxon man had two wives, one ablack-haired, red-skinned Indian squaw, the other a woolly-headed, sooty-skinned negress--and that instead of the children being mulattoesof brown or dusky tints, mingling the separate characteristics of theirparents in varying degrees, all the boys should be pure Saxon boys liketheir father, while the girls should altogether resemble their mothers. This would be thought a sufficiently wonderful fact; yet the phenomenahere brought forward as existing in the insect-world are still moreextraordinary; for each mother is capable not only of producing maleoffspring like the father, and female like herself, but also ofproducing other females exactly like her fellow-wife, and altogetherdiffering from herself. If an island could be stocked with a colony ofhuman beings having similar physiological idiosyncrasies with PapilioPammon or Papilio Ormenus, we should see white men living with yellow, red, and black women, and their offspring always reproducing the sametypes; so that at the end of many generations the men would remain purewhite, and the women of the same well-marked races as at thecommencement. The distinctive character therefore of dimorphism is this, that theunion of these distinct forms does not produce intermediate varieties, but reproduces the distinct forms unchanged. In simple varieties, on theother hand, as well as when distinct local forms or distinct species arecrossed, the offspring never resembles either parent exactly, but ismore or less intermediate between them. Dimorphism is thus seen to be aspecialized result of variation, by which new physiological phenomenahave been developed; the two should therefore, whenever possible, bekept separate. 3. _Local form, or variety. _--This is the first step in the transitionfrom variety to species. It occurs in species of wide range, when groupsof individuals have become partially isolated in several points of itsarea of distribution, in each of which a characteristic form has becomemore or less completely segregated. Such forms are very common in allparts of the world, and have often been classed by one author asvarieties, by another as species. I restrict the term to those caseswhere the difference of the forms is very slight, or where thesegregation is more or less imperfect. The best example in the presentgroup is Papilio Agamemnon, a species which ranges over the greater partof tropical Asia, the whole of the Malay archipelago, and a portion ofthe Australian and Pacific regions. The modifications are principally ofsize and form, and, though slight, are tolerably constant in eachlocality. The steps, however, are so numerous and gradual that it wouldbe impossible to define many of them, though the extreme forms aresufficiently distinct. Papilio Sarpedon presents somewhat similar butless numerous variations. 4. _Co-existing Variety. _--This is a somewhat doubtful case. It is whena slight but permanent and hereditary modification of form exists incompany with the parent or typical form, without presenting thoseintermediate gradations which would constitute it a case of simplevariability. It is evidently only by direct evidence of the two formsbreeding separately that this can be distinguished from dimorphism. Thedifficulty occurs in Papilio Jason, and P. Evemon, which inhabit thesame localities, and are almost exactly alike in form, size, andcolouration, except that the latter always wants a very conspicuous redspot on the under surface, which is found not only in P. Jason, but inall the allied species. It is only by breeding the two insects that itcan be determined whether this is a case of a co-existing variety or ofdimorphism. In the former case, however, the difference being constantand so very conspicuous and easily defined, I see not how we couldescape considering it as a distinct species. A true case of co-existingforms would, I consider, be produced, if a slight variety had becomefixed as a local form, and afterwards been brought into contact with theparent species, with little or no intermixture of the two; and suchinstances do very probably occur. 5. _Race or subspecies. _--These are local forms completely fixed andisolated; and there is no possible test but individual opinion todetermine which of them shall be considered as species and whichvarieties. If stability of form and "_the constant transmission of somecharacteristic peculiarity of organization_" is the test of a species(and I can find no other test that is more certain than individualopinion) then every one of these fixed races, confined as they almostalways are to distinct and limited areas, must be regarded as a species;and as such I have in most cases treated them. The various modificationsof Papilio Ulysses, P. Peranthus, P. Codrus, P. Eurypilus, P. Helenus, &c. , are excellent examples; for while some present great andwell-marked, others offer slight and inconspicuous differences, yet inall cases these differences seem equally fixed and permanent. If, therefore, we call some of these forms species, and others varieties, weintroduce a purely arbitrary distinction, and shall never be able todecide where to draw the line. The races of Papilio Ulysses, forexample, vary in amount of modification from the scarcely differing NewGuinea form to those of Woodlark Island and New Caledonia, but all seemequally constant; and as most of these had already been named anddescribed as species, I have added the New Guinea form under the name ofP. Autolycus. We thus get a little group of Ulyssine Papilios, the wholecomprised within a very limited area, each one confined to a separateportion of that area, and, though differing in various amounts, eachapparently constant. Few naturalists will doubt that all these may andprobably have been derived from a common stock, and therefore it seemsdesirable that there should be a unity in our method of treating them;either call them all _varieties_ or all _species_. Varieties, however, continually get overlooked; in lists of species they are oftenaltogether unrecorded; and thus we are in danger of neglecting theinteresting phenomena of variation and distribution which they present. I think it advisable, therefore, to name all such forms; and those whowill not accept them as species may consider them as subspecies orraces. 6. _Species. _--Species are merely those strongly marked races or localforms which when in contact do not intermix, and when inhabitingdistinct areas are generally believed to have had a separate origin, andto be incapable of producing a fertile hybrid offspring. But as the testof hybridity cannot be applied in one case in ten thousand, and even ifit could be applied would prove nothing, since it is founded on anassumption of the very question to be decided--and as the test ofseparate origin is in every case inapplicable--and as, further, the testof non-intermixture is useless, except in those rare cases where themost closely allied species are found inhabiting the same area, it willbe evident that we have no means whatever of distinguishing so-called"true species" from the several modes of variation here pointed out, andinto which they so often pass by an insensible gradation. It is quitetrue that, in the great majority of cases, what we term "species" areso well marked and definite that there is no difference of opinion aboutthem; but as the test of a true theory is, that it accounts for, or atthe very least is not inconsistent with, the whole of the phenomena andapparent anomalies of the problem to be solved, it is reasonable to askthat those who deny the origin of species by variation and selectionshould grapple with the facts in detail, and show how the doctrine ofthe distinct origin and permanence of species will explain and harmonizethem. It has been recently asserted by Dr. J. E. Gray (in theProceedings of the Zoological Society for 1863, page 134), that thedifficulty of limiting species is in proportion to our ignorance, andthat just as groups or countries are more accurately known and studiedin greater detail the limits of species become settled. This statementhas, like many other general assertions, its portion of both truth anderror. There is no doubt that many uncertain species, founded on few orisolated specimens, have had their true nature determined by the studyof a good series of examples: they have been thereby established asspecies or as varieties; and the number of times this has occurred isdoubtless very great. But there are other, and equally trustworthycases, in which, not single species, but whole groups have, by the studyof a vast accumulation of materials, been proved to have no definitespecific limits. A few of these must be adduced. In Dr. Carpenter's"Introduction to the Study of the Foraminifera, " he states that "_thereis not a single specimen of plant or animal of which the range ofvariation has been studied by the collocation and comparison of so largea number of specimens as have passed under the review of Messrs. Williamson, Parker, Rupert Jones, and myself, in our studies of thetypes of this group_;" and the result of this extended comparison ofspecimens is stated to be, "_The range of variation is so great amongthe Foraminifera as to include not merely those differential characterswhich have been usually accounted_ SPECIFIC, _but also those upon whichthe greater part of the_ GENERA _of this group have been founded, andeven in some instances those of its_ ORDERS" (Foraminifera, Preface, x). Yet this same group had been divided by D'Orbigny and other authors intoa number of clearly defined _families_, _genera_, and _species_, whichthese careful and conscientious researches have shown to have beenalmost all founded on incomplete knowledge. Professor DeCandolle has recently given the results of an extensivereview of the species of Cupuliferæ. He finds that the best-knownspecies of oaks are those which produce most varieties and subvarieties;that they are often surrounded by provisional species; and, with thefullest materials at his command, two-thirds of the species he considersmore or less doubtful. His general conclusion is, that "_in botany thelowest series of groups, _ SUBVARIETIES, VARIETIES, _and_ RACES _are verybadly limited; these can be grouped into_ SPECIES _a little less vaguelylimited, which again can be formed into sufficiently precise_ GENERA. "This general conclusion is entirely objected to by the writer of thearticle in the "Natural History Review, " who, however, does not deny itsapplicability to the particular order under discussion, while this verydifference of opinion is another proof that difficulties in thedetermination of species do not, any more than in the higher groups, vanish with increasing materials and more accurate research. Another striking example of the same kind is seen in the genera Rubusand Rosa, adduced by Mr. Darwin himself; for though the amplestmaterials exist for a knowledge of these groups, and the most carefulresearch has been bestowed upon them, yet the various species have notthereby been accurately limited and defined so as to satisfy themajority of botanists. In Mr. Baker's revision of the British Roses, just published by the Linnæan Society, the author includes under thesingle species Rosa canina, no less than twenty-eight named _varieties_, distinguished by more or less constant characters and often confined tospecial localities; and to these are referred about seventy of the_species_ of Continental and British botanists. Dr. Hooker seems to have found the same thing in his study of the Arcticflora. For though he has had much of the accumulated materials of hispredecessors to work upon, he continually expresses himself as unable todo more than group the numerous and apparently fluctuating forms intomore or less imperfectly defined species. In his paper on the"Distribution of Arctic Plants, " (Trans. Linn. Soc. Xxiii. , p. 310) Dr. Hooker says:--"The most able and experienced descriptive botanists varyin their estimate of the value of the 'specific term' to a much greaterextent than is generally supposed. " ... "I think I may safely affirmthat the 'specific term' has three different standard values, allcurrent in descriptive botany, but each more or less confined to oneclass of observers. " ... "This is no question of what is right or wrongas to the real value of the specific term; I believe each is rightaccording to the standard he assumes as the specific. " Lastly, I will adduce Mr. Bates's researches on the Amazons. Duringeleven years he accumulated vast materials, and carefully studied thevariation and distribution of insects. Yet he has shown that manyspecies of Lepidoptera, which before offered no special difficulties, are in reality most intricately combined in a tangled web of affinities, leading by such gradual steps from the slightest and least stablevariations to fixed races and well-marked species, that it is very oftenimpossible to draw those sharp dividing-lines which it is supposed thata careful study and full materials will always enable us to do. These few examples show, I think, that in every department of naturethere occur instances of the instability of specific form, which theincrease of materials aggravates rather than diminishes. And it must beremembered that the naturalist is rarely likely to err on the side ofimputing greater indefiniteness to species than really exists. There isa completeness and satisfaction to the mind in defining and limitingand naming a species, which leads us all to do so whenever weconscientiously can, and which we know has led many collectors to rejectvague intermediate forms as destroying the symmetry of their cabinets. We must therefore consider these cases of excessive variation andinstability as being thoroughly well established; and to the objectionthat, after all, these cases are but few compared with those in whichspecies can be limited and defined, and are therefore merely exceptionsto a general rule, I reply that a true law embraces all apparentexceptions, and that to the great laws of nature there are no realexceptions--that what appear to be such are equally results of law, andare often (perhaps indeed always) those very results which are mostimportant as revealing the true nature and action of the law. It is forsuch reasons that naturalists now look upon the study of _varieties_ asmore important than that of well-fixed species. It is in the former thatwe see nature still at work, in the very act of producing thosewonderful modifications of form, that endless variety of colour, andthat complicated harmony of relations, which gratify every sense andgive occupation to every faculty of the true lover of nature. _Variation as specially influenced by Locality. _ The phenomena of variation as influenced by locality have not hithertoreceived much attention. Botanists, it is true, are acquainted with theinfluences of climate, altitude, and other physical conditions, inmodifying the forms and external characteristics of plants; but I am notaware that any peculiar influence has been traced to locality, independent of climate. Almost the only case I can find recorded ismentioned in that repertory of natural-history facts, "The Origin ofSpecies, " viz. That herbaceous groups have a tendency to become arborealin islands. In the animal world, I cannot find that any facts have beenpointed out as showing the special influence of locality in giving apeculiar _facies_ to the several disconnected species that inhabit it. What I have to adduce on this matter will therefore, I hope, possesssome interest and novelty. On examining the closely allied species, local forms, and varietiesdistributed over the Indian and Malayan regions, I find that larger orsmaller districts, or even single islands, give a special character tothe majority of their Papilionidæ. For instance: 1. The species of theIndian region (Sumatra, Java, and Borneo) are almost invariably smallerthan the allied species inhabiting Celebes and the Moluccas; 2. Thespecies of New Guinea and Australia are also, though in a less degree, smaller than the nearest species or varieties of the Moluccas; 3. In theMoluccas themselves the species of Amboyna are the largest; 4. Thespecies of Celebes equal or even surpass in size those of Amboyna; 5. The species and varieties of Celebes possess a striking character in theform of the anterior wings, different from that of the allied speciesand varieties of all the surrounding islands; 6. Tailed species in Indiaor the Indian region become tailless as they spread eastward through thearchipelago; 7. In Amboyna and Ceram the females of several species aredull-coloured, while in the adjacent islands they are more brilliant. _Local variation of Size. _--Having preserved the finest and largestspecimens of Butterflies in my own collection, and having always takenfor comparison the largest specimens of the same sex, I believe that thetables I now give are sufficiently exact. The differences of expanse ofwings are in most cases very great, and are much more conspicuous in thespecimens themselves than on paper. It will be seen that no less thanfourteen Papilionidæ inhabiting Celebes and the Moluccas are fromone-third to one-half greater in extent of wing than the allied speciesrepresenting them in Java, Sumatra, and Borneo. Six species inhabitingAmboyna are larger than the closely allied forms of the northernMoluccas and New Guinea by about one-sixth. These include almost everycase in which closely allied species can be compared. Species of Papilionidæ of the Closely allied species of Java and Moluccas and Celebes (large). The Indian region (small). Expanse. Expanse. Inches. Inches. Ornithoptera (Helena { O. Pompeus 5·8 Amboyna) 7·6 { O. Amphrisius 6·0 Papilio Adamantius } (Celebes) 5·8 } P. Lorquinianus } P. Peranthus 3·8 (Moluccas) 4·8 } P. Blumei (Celebes) 5·4 P. Brama 4·0 P. Alphenor (Celebes) 4·8 P. Theseus 3·6 P. Gigon (Celebes) 5·4 P. Demolion 4·0 P. Deucalion (Celebes) 4·6 P. Macareus 3·7 P. Agamemnon, var. (Celebes) 4·4 P. Agamemnon, var. 3·8 P. Eurypilus (Moluccas) 4·0 } P. Jason 3·4 P. Telephus (Celebes) 4·3 } P. Ægisthus (Moluccas) 4·4 P. Rama 3·2 P. Milon (Celebes) 4·4 P. Sarpedon 3·8 P. Androcles (Celebes) 4·8 P. Antiphates 3·7 P. Polyphontes (Celebes) 4·6 P. Diphilus 3·9 Leptocircus Ennius (Celebes) 2·0 L. Meges 1·8 Species inhabiting Amboyna Allied species of New Guinea and (large). The North Moluccas (smaller). Papilio Ulysses 6·1 { P. Autolycus 5·2 { P. Telegonus 4·0 P. Polydorus 4·9 P. Leodamas 4·0 P. Deiphobus 6·8 P. Deiphontes 5·8 P. Gambrisius 6·4 { P. Ormenus 5·6 { P. Tydeus 6·0 P. Codrus 5·1 P. Codrus, var. Papuensis 4·3 Ornithoptera Priamus, Ornithoptera Poseidon, (male) 8·3 (male) 7·0 _Local variation of Form. _--The differences of form are equally clear. Papilio Pammon everywhere on the continent is tailed in both sexes. InJava, Sumatra, and Borneo, the closely allied P. Theseus has a veryshort tail, or tooth only, in the male, while in the females the tail isretained. Further east, in Celebes and the South Moluccas, the hardlyseparable P. Alphenor has quite lost the tail in the male, while thefemale retains it, but in a narrower and less spatulate form. A littlefurther, in Gilolo, P. Nicanor has completely lost the tail in bothsexes. Papilio Agamemnon exhibits a somewhat similar series of changes. InIndia it is always tailed; in the greater part of the archipelago it hasa very short tail; while far east, in New Guinea and the adjacentislands, the tail has almost entirely disappeared. In the Polydorus-group two species, P. Antiphus and P. Diphilus, inhabiting India and the Indian region, are tailed, while the two whichtake their place in the Moluccas, New Guinea, and Australia, P. Polydorus and P. Leodamas, are destitute of tail, the species furthesteast having lost this ornament the most completely. Western species, Tailed. Allied Eastern species not Tailed. Papilio Pammon (India) P. Thesus (Islands) minute tail. P. Agamemnon, var. (India) P. Agamemnon, var. (Islands). P. Antiphus (India, Java) P. Polydorus (Moluccas). P. Diphilus (India, Java) P. Leodamas (New Guinea). The most conspicuous instance of local modification of form, however, isexhibited in the island of Celebes, which in this respect, as in someothers, stands alone and isolated in the whole archipelago. Almost everyspecies of Papilio inhabiting Celebes has the wings of a peculiar shape, which distinguishes them at a glance from the allied species of everyother island. This peculiarity consists, first, in the upper wings beinggenerally more elongate and falcate; and secondly, in the costa oranterior margin being much more curved, and in most instances exhibitingnear the base an abrupt bend or elbow, which in some species is veryconspicuous. This peculiarity is visible, not only when the Celebesianspecies are compared with their small-sized allies of Java and Borneo, but also, and in an almost equal degree, when the large forms of Amboynaand the Moluccas are the objects of comparison, showing that this isquite a distinct phenomenon from the difference of size which has justbeen pointed out. In the following Table I have arranged the chief Papilios of Celebes inthe order in which they exhibit this characteristic form mostprominently. Papilios of Celebes, having the Closely allied Papilios of the wings falcate or with abruptly surrounding islands, with less curved costa. Wings and slightly falcate curved costa. 1. P. Gigon P. Demolion (Java). 2. P. Pamphylus P. Jason (Sumatra). 3. P. Milon P. Sarpedon (Moluccas, Java). 4. P. Agamemnon, var. P. Agamemnon, var. (Borneo). 5. P. Adamantius P. Peranthus (Java). 6. P. Ascalaphus P. Deiphontes (Gilolo). 7. P. Sataspes P. Helenus (Java). 8. P. Blumei P. Brama (Sumatra). 9. P. Androcles P. Antiphates (Borneo). 10. P. Rhesus P. Aristæus (Moluccas). 11. P. Theseus, var. (male) P. Thesus (male) (Java). 12. P. Codrus, var. P. Codrus (Moluccas). 13. P. Encelades P. Leucothoë (Malacca). It thus appears that every species of Papilio exhibits this peculiarform in a greater or less degree, except one, P. Polyphontes, allied toP. Diphilus of India and P. Polydorus of the Moluccas. This fact Ishall recur to again, as I think it helps us to understand something ofthe causes that may have brought about the phenomenon we areconsidering. Neither do the genera Ornithoptera and Leptocircus exhibitany traces of this peculiar form. In several other families ofButterflies this characteristic form reappears in a few species. In thePieridæ the following species, all peculiar to Celebes, exhibit itdistinctly:-- 1. Pieris Eperia compared with P. Coronis (Java). 2. Thyca Zebuda " " Thyca Descombesi (India). 3. T. Rosenbergii " " T. Hyparete (Java). 4. Tachyris Hombronii " " T. Lyncida. 5. T. Lycaste " " T. Lyncida. 6. T. Zarinda " " T. Nero (Malacca). 7. T. Ithome " " T. Nephele. 8. Eronia tritæa " " Eronia Valeria (Java). 9. Iphias Glaucippe, var. " " Iphias Glaucippe (Java). The species of Terias, one or two Pieris, and the genus Callidryas donot exhibit any perceptible change of form. In the other families there are but few similar examples. The followingare all that I can find in my collection:-- Cethosia Æole compared with Cethosia Biblis (Java). Eurhinia megalonice " " Eurhinia Polynice (Borneo). Limenitis Limire " " Limenitis Procris (Java). Cynthia Arsinoë, var. " " Cynthia Arsinoë (Java, Sumatra, Borneo) All these belong to the family of the Nymphalidæ. Many other genera ofthis family, as Diadema, Adolias, Charaxes, and Cyrestis, as well as theentire families of the Danaidæ, Satyridæ, Lycænidæ, and Hesperidæ, present no examples of this peculiar form of the upper wing in theCelebesian species. _Local variations of Colour. _--In Amboyna and Ceram the female of thelarge and handsome Ornithoptera Helena has the large patch on the hindwings constantly of a pale dull ochre or buff colour, while in thescarcely distinguishable varieties from the adjacent islands of Bouruand New Guinea, it is of a golden yellow, hardly inferior in brilliancyto its colour in the male sex. The female of Ornithoptera Priamus(inhabiting Amboyna and Ceram exclusively) is of a pale dusky browntint, while in all the allied species the same sex is nearly black withcontrasted white markings. As a third example, the female of PapilioUlysses has the blue colour obscured by dull and dusky tints, while inthe closely allied species from the surrounding islands, the females areof almost as brilliant an azure blue as the males. A parallel case tothis is the occurrence, in the small islands of Goram, Matabello, Ké, and Aru, of several distinct species of Euploea and Diadema, having broadbands or patches of white, which do not exist in any of the alliedspecies from the larger islands. These facts seem to indicate some localinfluence in modifying colour, as unintelligible and almost asremarkable as that which has resulted in the modifications of formpreviously described. _Remarks on the facts of Local variation. _ The facts now brought forward seem to me of the highest interest. We seethat almost all the species in two important families of the Lepidoptera(Papilionidæ and Pieridæ) acquire, in a single island, a characteristicmodification of form distinguishing them from the allied species andvarieties of all the surrounding islands. In other equally extensivefamilies no such change occurs, except in one or two isolated species. However we may account for these phenomena, or whether we may be quiteunable to account for them, they furnish, in my opinion, a strongcorroborative testimony in favour of the doctrine of the origin ofspecies by successive small variations; for we have here slightvarieties, local races, and undoubted species, all modified in exactlythe same manner, indicating plainly a common cause producing identicalresults. On the generally received theory of the original distinctnessand permanence of species, we are met by this difficulty: one portion ofthese curiously modified forms are admitted to have been produced byvariation and some natural action of local conditions; whilst the otherportion, differing from the former only in degree, and connected withthem by insensible gradations, are said to have possessed thispeculiarity of form at their first creation, or to have derived it fromunknown causes of a totally distinct nature. Is not the _à priori_evidence in favour of an identity of the causes that have produced suchsimilar results? and have we not a right to call upon our opponents forsome proofs of their own doctrine, and for an explanation of itsdifficulties, instead of their assuming that they are right, and layingupon us the burthen of disproof? Let us now see if the facts in question do not themselves furnish someclue to their explanation. Mr. Bates has shown that certain groups ofbutterflies have a defence against insectivorous animals, independent ofswiftness of motion. These are generally very abundant, slow, and weakfliers, and are more or less the objects of mimicry by other groups, which thus gain an advantage in a freedom from persecution similar tothat enjoyed by those they resemble. Now the only Papilios which havenot in Celebes acquired the peculiar form of wing, belong to a groupwhich is imitated both by other species of Papilio and by Moths of thegenus Epicopeia. This group is of weak and slow flight; and we maytherefore fairly conclude that it possesses some means of defence(probably in a peculiar odour or taste) which saves it from attack. Nowthe arched costa and falcate form of wing is generally supposed to giveincreased powers of flight, or, as seems to me more probable, greaterfacility in making sudden turnings, and thus baffling a pursuer. But themembers of the Polydorus-group (to which belongs the only unchangedCelebesian Papilio), being already guarded against attack, have no needof this increased power of wing; and "natural selection" would thereforehave no tendency to produce it. The whole family of Danaidæ are in thesame position: they are slow and weak fliers; yet they abound in speciesand individuals, and are the objects of mimicry. The Satyridæ have alsoprobably a means of protection--perhaps their keeping always near theground and their generally obscure colours; while the Lycænidæ andHesperidæ may find security in their small size and rapid motions. Inthe extensive family of the Nymphalidæ, however, we find that several ofthe larger species, of comparatively feeble structure, have their wingsmodified (Cethosia, Limenitis, Junonia, Cynthia), while the large-bodiedpowerful species, which have all an excessively rapid flight, haveexactly the same form of wing in Celebes as in the other islands. On thewhole, therefore, we may say that all the butterflies of rather largesize, conspicuous colours, and not very swift flight have been affectedin the manner described, while the smaller sized and obscure groups, aswell as those which are the objects of mimicry, and also those ofexceedingly swift flight have remained unaffected. It would thus appear as if there must be (or once have been) in theisland of Celebes, some peculiar enemy to these larger-sized butterflieswhich does not exist, or is less abundant, in the surrounding islands. Increased powers of flight, or rapidity of turning, was advantageous inbaffling this enemy; and the peculiar form of wing necessary to givethis would be readily acquired by the action of "natural selection" onthe slight variations of form that are continually occurring. Such an enemy one would naturally suppose to be an insectivorous bird;but it is a remarkable fact that most of the genera of Fly-catchersof Borneo and Java on the one side (Muscipeta, Philentoma, ) and ofthe Moluccas on the other (Monarcha, Rhipidura), are almost entirelyabsent from Celebes. Their place seems to be supplied by theCaterpillar-catchers (Graucalus, Campephaga, &c. ), of which six or sevenspecies are known from Celebes and are very numerous in individuals. Wehave no positive evidence that these birds pursue butterflies on thewing, but it is highly probable that they do so when other food isscarce. Mr. Bates has suggested to me that the larger Dragonflies(Æshna, &c. ) prey upon butterflies; but I did not notice that they weremore abundant in Celebes than elsewhere. However this may be, the faunaof Celebes is undoubtedly highly peculiar in every department of whichwe have any accurate knowledge; and though we may not be ablesatisfactorily to trace how it has been effected, there can, I think, belittle doubt that the singular modification in the wings of so many ofthe butterflies of that island is an effect of that complicated actionand reaction of all living things upon each other in the struggle forexistence, which continually tends to readjust disturbed relations, andto bring every species into harmony with the varying conditions of thesurrounding universe. But even the conjectural explanation now given fails us in the othercases of local modification. Why the species of the Western islandsshould be smaller than those further east, --why those of Amboyna shouldexceed in size those of Gilolo and New Guinea--why the tailed speciesof India should begin to lose that appendage in the islands, and retainno trace of it on the borders of the Pacific, --and why, in threeseparate cases, the females of Amboyna species should be less gailyattired than the corresponding females of the surrounding islands, --arequestions which we cannot at present attempt to answer. That theydepend, however, on some general principle is certain, because analogousfacts have been observed in other parts of the world. Mr. Bates informsme that, in three distinct groups, Papilios which on the Upper Amazonand in most other parts of South America have spotless upper wingsobtain pale or white spots at Pará and on the Lower Amazon; and alsothat the Æneas-group of Papilios never have tails in the equatorialregions and the Amazons valley, but gradually acquire tails in manycases as they range towards the northern or southern tropic. Even inEurope we have somewhat similar facts; for the species and varieties ofbutterflies peculiar to the island of Sardinia are generally smaller andmore deeply coloured than those of the mainland, and the same hasrecently been shown to be the case with the common tortoiseshellbutterfly in the Isle of Man; while Papilio Hospiton, peculiar to theformer island, has lost the tail, which is a prominent feature of theclosely allied P. Machaon. Facts of a similar nature to those now brought forward would no doubt befound to occur in other groups of insects, were local faunas carefullystudied in relation to those of the surrounding countries; and theyseem to indicate that climate and other physical causes have, in somecases, a very powerful effect in modifying specific form and colour, andthus directly aid in producing the endless variety of nature. _Mimicry. _ Having fully discussed this subject in the preceding essay, I have onlyto adduce such illustrations of it, as are furnished by the EasternPapilionidæ, and to show their bearing upon the phenomena of variationalready mentioned. As in America, so in the Old World, species ofDanaidæ are the objects which the other families most often imitate. Butbesides these, some genera of Morphidæ and one section of the genusPapilio are also less frequently copied. Many species of Papilio mimicother species of these three groups so closely that they areundistinguishable when on the wing; and in every case the pairs whichresemble each other inhabit the same locality. The following list exhibits the most important and best marked cases ofmimicry which occur among the Papilionidæ of the Malayan region andIndia:-- Mimickers. Species mimicked. Common habitat. DANAIDÆ. 1. Papilio paradoxa Euploea Midamus } Sumatra, &c. (male & female) (male & female) } 2. P. Caunus E. Rhadamanthus Borneo and Sumatra. 3. P. Thule Danais sobrina New Guinea. 4. P. Macareus D. Aglaia Malacca, Java 5. Papilio Agestor Danais Tytia Northern India. 6. P. Idæoides Hestia Leuconoë Philippines. 7. P. Delessertii Ideopsis daos Penang. MORPHIDÆ. 8. P. Pandion Drusilla bioculata New Guinea (female) PAPILIO (POLYDORUS- and COON-groups). 9. P. Pammon (Romulus, Papilio Hector India. Female) 10. P. Theseus, var. P. Antiphus Sumatra, Borneo. (female) 11. P. Theseus, var. P. Diphilus Sumatra, Java. (female) 12. P. Memnon, var. P. Coon Sumatra. (Achates, female) 13. P. Androgeus, var. P. Doubledayi Northern India. (Achates, female) 14. P. Oenomaus P. Liris Timor. (female) We have, therefore, fourteen species or marked varieties of Papilio, which so closely resemble species of other groups in their respectivelocalities, that it is not possible to impute the resemblance toaccident. The first two in the list (Papilio paradoxa and P. Caunus) areso exactly like Euploea Midamus and E. Rhadamanthus on the wing, thatalthough they fly very slowly, I was quite unable to distinguish them. The first is a very interesting case, because the male and female differconsiderably, and each mimics the corresponding sex of the Euploea. Anew species of Papilio which I discovered in New Guinea resembles Danaissobrina, from the same country, just as Papilio Marcareus resemblesDanais Aglaia in Malacca, and (according to Dr. Horsfield's figure)still more closely in Java. The Indian Papilio Agestor closely imitatesDanais Tytia, which has quite a different style of colouring from thepreceding; and the extraordinary Papilio Idæoides from the PhilippineIslands, must, when on the wing, perfectly resemble the Hestia Leuconoëof the same region, as also does the Papilio Delessertii imitate theIdeopsis daos from Penang. Now in every one of these cases the Papiliosare very scarce, while the Danaidæ which they resemble are exceedinglyabundant--most of them swarming so as to be a positive nuisance to thecollecting entomologist by continually hovering before him when he is insearch of newer and more varied captures. Every garden, every roadside, the suburbs of every village are full of them, indicating very clearlythat their life is an easy one, and that they are free from persecutionby the foes which keep down the population of less favoured races. Thissuperabundant population has been shown by Mr. Bates to be a generalcharacteristic of all American groups and species which are objects ofmimicry; and it is interesting to find his observations confirmed byexamples on the other side of the globe. The remarkable genus Drusilla, a group of pale-coloured butterflies, more or less adorned with ocellate spots, is also the object of mimicryby three distinct genera (Melanitis, Hyantis, and Papilio). Theseinsects, like the Danaidæ, are abundant in individuals, have a veryweak and slow flight, and do not seek concealment, or appear to have anymeans of protection from insectivorous creatures. It is natural toconclude, therefore, that they have some hidden property which savesthem from attack; and it is easy to see that when any other insects, bywhat we call accidental variation, come more or less remotely toresemble them, the latter will share to some extent in their immunity. An extraordinary dimorphic form of the female of Papilio Ormenus hascome to resemble the Drusillas sufficiently to be taken for one of thatgroup at a little distance; and it is curious that I captured one ofthese Papilios in the Aru Islands hovering along the ground, andsettling on it occasionally, just as it is the habit of the Drusillas todo. The resemblance in this case is only general; but this form ofPapilio varies much, and there is therefore material for naturalselection to act upon, so as ultimately to produce a copy as exact as inthe other cases. The eastern Papilios allied to Polydorus, Coon, and Philoxenus, form anatural section of the genus resembling, in many respects, theÆneas-group of South America, which they may be said to represent in theEast. Like them, they are forest insects, have a low and weak flight, and in their favourite localities are rather abundant in individuals;and like them, too, they are the objects of mimicry. We may conclude, therefore, that they possess some hidden means of protection, whichmakes it useful to other insects to be mistaken for them. The Papilios which resemble them belong to a very distinct section ofthe genus, in which the sexes differ greatly; and it is those femalesonly which differ most from the males, and which have already beenalluded to as exhibiting instances of dimorphism, which resemble speciesof the other group. The resemblance of P. Romulus to P. Hector is, in some specimens, veryconsiderable, and has led to the two species being placed following eachother in the British Museum Catalogues and by Mr. E. Doubleday. I haveshown, however, that P. Romulus is probably a dimorphic form of thefemale P. Pammon, and belongs to a distinct section of the genus. The next pair, Papilio Theseus, and P. Antiphus, have been united as onespecies both by De Haan and in the British Museum Catalogues. Theordinary variety of P. Theseus found in Java almost as nearly resemblesP. Diphilus, inhabiting the same country. The most interesting case, however, is the extreme female form of P. Memnon (figured by Cramerunder the name of P. Achates), which has acquired the general form andmarkings of P. Coon, an insect which differs from the ordinary male P. Memnon, as much as any two species which can be chosen in this extensiveand highly varied genus; and, as if to show that this resemblance is notaccidental, but is the result of law, when in India we find a speciesclosely allied to P. Coon, but with red instead of yellow spots (P. Doubledayi), the corresponding variety of P. Androgeus (P. Achates, Cramer, 182, A, B, ) has acquired exactly the same peculiarity of havingred spots instead of yellow. Lastly, in the island of Timor, the femaleof P. Oenomaus (a species allied to P. Memnon) resembles so closely P. Liris (one of the Polydorus-group), that the two, which were often seenflying together, could only be distinguished by a minute comparisonafter being captured. The last six cases of mimicry are especially instructive, because theyseem to indicate one of the processes by which dimorphic forms have beenproduced. When, as in these cases, one sex differs much from the other, and varies greatly itself, it may happen that occasionally individualvariations will occur having a distant resemblance to groups which arethe objects of mimicry, and which it is therefore advantageous toresemble. Such a variety will have a better chance of preservation; theindividuals possessing it will be multiplied; and their accidentallikeness to the favoured group will be rendered permanent by hereditarytransmission, and, each successive variation which increases theresemblance being preserved, and all variations departing from thefavoured type having less chance of preservation, there will in timeresult those singular cases of two or more isolated and fixed forms, bound together by that intimate relationship which constitutes them thesexes of a single species. The reason why the females are more subjectto this kind of modification than the males is, probably, that theirslower flight, when laden with eggs, and their exposure to attack whilein the act of depositing their eggs upon leaves, render it especiallyadvantageous for them to have some additional protection. This they atonce obtain by acquiring a resemblance to other species which, fromwhatever cause, enjoy a comparative immunity from persecution. _Concluding remarks on Variation in Lepidoptera. _ This summary of the more interesting phenomena of variation presented bythe eastern Papilionidæ is, I think, sufficient to substantiate myposition, that the Lepidoptera are a group that offer especialfacilities for such inquiries; and it will also show that they haveundergone an amount of special adaptive modification rarely equalledamong the more highly organized animals. And, among the Lepidoptera, thegreat and pre-eminently tropical families of Papilionidæ and Danaidæseem to be those in which complicated adaptations to the surroundingorganic and inorganic universe have been most completely developed, offering in this respect a striking analogy to the equallyextraordinary, though totally different, adaptations which presentthemselves in the Orchideæ, the only family of plants in which mimicryof other organisms appears to play any important part, and the only onein which cases of conspicuous polymorphism occur; for as such we mustclass the male, female, and hermaphrodite forms of Catasetumtridentatum, which differ so greatly in form and structure that theywere long considered to belong to three distinct genera. _Arrangement and Geographical Distribution of the Malayan Papilionidæ_. _Arrangement. _--Although the species of Papilionidæ inhabiting theMalayan region are very numerous, they all belong to three out of thenine genera into which the family is divided. One of the remaininggenera (Eurycus) is restricted to Australia, and another (Teinopalpus)to the Himalayan Mountains, while no less than four (Parnassius, Doritis, Thais, and Sericinus) are confined to Southern Europe and tothe mountain-ranges of the Palæarctic region. The genera Ornithoptera and Leptocircus are highly characteristic ofMalayan entomology, but are uniform in character and of small extent. The genus Papilio, on the other hand, presents a great variety of forms, and is so richly represented in the Malay Islands, that more thanone-fourth of all the known species are found there. It becomesnecessary, therefore, to divide this genus into natural groups before wecan successfully study its geographical distribution. Owing principally to Dr. Horsfield's observations in Java, we areacquainted with a considerable number of the larvæ of Papilios; andthese furnish good characters for the primary division of the genus intonatural groups. The manner in which the hinder wings are plaited orfolded back at the abdominal margin, the size of the anal valves, thestructure of the antennæ, and the form of the wings are also of muchservice, as well as the character of the flight and the style ofcolouration. Using these characters, I divide the Malayan Papilios intofour sections, and seventeen groups, as follows:-- Genus ORNITHOPTERA. a. Priamus-group. } Black and Green. C. Brookeanus-group. } b. Pompeus-group. Black and yellow. Genus PAPILIO. A. Larvæ short, thick, with numerous fleshy tubercles; of a purplish colour. a. Nox-group. Abdominal fold in male very large; anal valves small, but swollen; antennæ moderate; wings entire, or tailed; includes the Indian Philoxenus-group. B. Coon-group. Abdominal fold in male small; anal valves small, but swollen; antennæ moderate; wings tailed. C. Polydorus-group. Abdominal fold in male small, or none; anal valves small or obsolete, hairy; wings tailed or entire. B. Larvæ with third segment swollen, transversely or obliquely banded; pupa much bent. Imago with abdominal margin in male plaited, but not reflexed; body weak; antennæ long; wings much dilated, often tailed. d. Ulysses-group. {Protenor-group (Indian) is e. Peranthus-group. {somewhat intermediate between f. Memnon-group. {these, and is nearest {to the Nox-group. G. Helenus-group. H. Erectheus-group. I. Pammon-group. K. Demolion-group. C. Larvæ subcylindrical, variously coloured. Imago with abdominal margin in male plaited, but not reflexed; body weak; antennæ short, with a thick curved club; wings entire. l. Erithonius-group. Sexes alike, larva and pupa something like those of P. Demolion. M. Paradoxa-group. Sexes different. N. Dissimilis-group. Sexes alike; larva bright-coloured; pupa straight, cylindric. D. Larvæ elongate, attenuate behind, and often bifid, with lateral and oblique pale stripes, green. Imago with the abdominal margin in male reflexed, woolly or hairy within; anal valves small, hairy; antennæ short, stout; body stout. o. Macareus-group. Hind wings entire. P. Antiphates-group. Hind wings much tailed (swallow-tails). Q. Eurypylus-group. Hind wings elongate or tailed. Genus LEPTOCIRCUS. Making, in all, twenty distinct groups of Malayan Papilionidæ. The first section of the genus Papilio (A) comprises insects which, though differing considerably in structure, having much generalresemblance. They all have a weak, low flight, frequent the mostluxuriant forest-districts, seem to love the shade, and are the objectsof mimicry by other Papilios. Section B consists of weak-bodied, large-winged insects, with anirregular wavering flight, and which, when resting on foliage, oftenexpand the wings, which the species of the other sections rarely ornever do. They are the most conspicuous and striking of easternButterflies. Section C consists of much weaker and slower-flying insects, oftenresembling in their flight, as well as in their colours, species ofDanaidæ. Section D contains the strongest-bodied and most swift-flying of thegenus. They love sunlight, and frequent the borders of streams and theedges of puddles, where they gather together in swarms consisting ofseveral species, greedily sucking up the moisture, and, when disturbed, circling round in the air, or flying high and with great strength andrapidity. _Geographical Distribution. _--One hundred and thirty species of MalayanPapilionidæ are now known within the district extending from the Malaypeninsula, on the north-west, to Woodlark Island, near New Guinea, onthe south-east. The exceeding richness of the Malayan region in these fine insects isseen by comparing the number of species found in the different tropicalregions of the earth. From all Africa only 33 species of Papilio areknown; but as several are still undescribed in collections, we may raisetheir number to about 40. In all tropical Asia there are at presentdescribed only 65 species, and I have seen in collections but two orthree which have not yet been named. In South America, south of Panama, there are 150 species, or about one-seventh more than are yet known fromthe Malayan region; but the area of the two countries is very different;for while South America (even excluding Patagonia) contains 5, 000, 000square miles, a line encircling the whole of the Malayan islands wouldonly include an area of 2, 700, 000 square miles, of which the land-areawould be about 1, 000, 000 square miles. This superior richness is partlyreal and partly apparent. The breaking up of a district into smallisolated portions, as in an archipelago, seems highly favourable to thesegregation and perpetuation of local peculiarities in certain groups;so that a species which on a continent might have a wide range, andwhose local forms, if any, would be so connected together that it wouldbe impossible to separate them, may become by isolation reduced to anumber of such clearly defined and constant forms that we are obliged tocount them as species. From this point of view, therefore, the greaterproportionate number of Malayan species may be considered as apparentonly. Its true superiority is shown, on the other hand, by thepossession of three genera and twenty groups of Papilionidæ against asingle genus and eight groups in South America, and also by the muchgreater average size of the Malayan species. In most other families, however, the reverse is the case, the South American Nymphalidæ, Satyridæ, and Erycinidæ far surpassing those of the East in number, variety, and beauty. The following list, exhibiting the range and distribution of each group, will enable us to study more easily their internal and externalrelations. _Range of the Groups of Malayan Papilionidæ. _ Ornithoptera. 1. Priamus-group. Moluccas to Woodlark Island 5 species. 2. Pompeus-group. Himalayas to New Guinea, (Celebes, maximum) 11" 3. Brookeana-group. Sumatra and Borneo 1" Papilio. 4. Nox-group. North India, Java, and Philippines 5 species 5. Coon-group. North India to Java 2" 6. Polydorus-group. India to New Guinea and Pacific 7" 7. Ulysses-group. Celebes to New Caledonia 4" 8. Peranthus-group. India to Timor and Moluccas (India, maximum) 9" 9. Memnon-group. India to Timor and Moluccas (Java, maximum) 10" 10. Helenus-group. Africa and India to New Guinea 11" 11. Pammon-group. India to Pacific and Australia 9" 12. Erectheus-group. Celebes to Australia 2" 13. Demolion-group. India to Celebes 2" 14. Erithonius-group. Africa, India, Australia 1" 15. Paradoxa-group. India to Java (Borneo, maximum) 5" 16. Dissimilis-group. India to Timor (India, maximum) 2" 17. Macareus-group. India to New Guinea 10" 18. Antiphates-group. Widely distributed 8" 19. Eurypylus-group. India to Australia 15" Leptocircus. 20. Leptocircus-group. India to Celebes 4" This Table shows the great affinity of the Malayan with the IndianPapilionidæ, only three out of the twenty groups ranging beyond, intoAfrica, Europe, or America. The limitation of groups to the Indo-Malayanor Austro-Malayan divisions of the archipelago, which is so well markedin the higher animals, is much less conspicuous in insects, but is shownin some degree by the Papilionidæ. The following groups are eitheralmost or entirely restricted to one portion of the archipelago:-- _Indo-Malayan Region. _ _Austro-Malayan Region. _ Nox-group. Priamus-group. Coon-group. Ulysses-group. Macareus-group (nearly). Erechtheus-group. Paradoxa-group. Dissimilis-group (nearly). Brookeanus-group. LEPTOCIRCUS (genus). The remaining groups, which range over the whole archipelago, are, inmany cases, insects of very powerful flight, or they frequent openplaces and the sea-beach, and are thus more likely to get blown fromisland to island. The fact that three such characteristic groups asthose of Priamus, Ulysses, and Erechtheus are strictly limited to theAustralian region of the archipelago, while five other groups are withequal strictness confined to the Indian region, is a strongcorroboration of that division which has been founded almost entirely onthe distribution of Mammalia and Birds. If the various Malayan islands have undergone recent changes of level, and if any of them have been more closely united within the period ofexisting species than they are now, we may expect to find indications ofsuch changes in community of species between islands now widelyseparated; while those islands which have long remained isolated wouldhave had time to acquire peculiar forms by a slow and natural process ofmodification. An examination of the relations of the species of the adjacent islands, will thus enable us to correct opinions formed from a mere considerationof their relative positions. For example, looking at a map of thearchipelago, it is almost impossible to avoid the idea that Java andSumatra have been recently united; their present proximity is so great, and they have such an obvious resemblance in their volcanic structure. Yet there can be little doubt that this opinion is erroneous, and thatSumatra has had a more recent and more intimate connexion with Borneothan it has had with Java. This is strikingly shown by the mammals ofthese islands--very few of the species of Java and Sumatra beingidentical, while a considerable number are common to Sumatra and Borneo. The birds show a somewhat similar relationship; and we shall find thatthe distribution of the Papilionidæ tells exactly the same tale. Thus:-- Sumatra has 21 species } Borneo " 30 " } 20 sp. Common to both islands; Sumatra " 21 " } Java " 28 " } 11 sp. Common to both islands; Borneo " 30 " } Java " 28 " } 20 sp. Common to both islands; showing that both Sumatra and Java have a much closer relationship toBorneo than they have to each other--a most singular and interestingresult, when we consider the wide separation of Borneo from them both, and its very different structure. The evidence furnished by a singlegroup of insects would have had but little weight on a point of suchmagnitude if standing alone; but coming as it does to confirm deductionsdrawn from whole classes of the higher animals, it must be admitted tohave considerable value. We may determine in a similar manner the relations of the differentPapuan Islands to New Guinea. Of thirteen species of Papilionidæobtained in the Aru Islands, six were also found in New Guinea, andseven not. Of nine species obtained at Waigiou, six were New Guinea, andthree not. The five species found at Mysol were all New Guinea species. Mysol, therefore, has closer relations to New Guinea than the otherislands; and this is corroborated by the distribution of the birds, ofwhich I will only now give one instance. The Paradise Bird found inMysol is the common New Guinea species, while the Aru Islands andWaigiou have each a species peculiar to themselves. The large island of Borneo, which contains more species of Papilionidæthan any other in the archipelago, has nevertheless only three peculiarto itself; and it is quite possible, and even probable, that one ofthese may be found in Sumatra or Java. The last-named island has alsothree species peculiar to it; Sumatra has not one, and the peninsula ofMalacca only two. The identity of species is even greater than in birdsor in most other groups of insects, and points very strongly to a recentconnexion of the whole with each other and the continent. _Remarkable Peculiarities of the Island of Celebes. _ If we now pass to the next island (Celebes), separated from those lastmentioned by a strait not wider than that which divides them from eachother, we have a striking contrast; for with a total number of speciesless than either Borneo or Java, no fewer than eighteen are absolutelyrestricted to it. Further east, the large islands of Ceram and NewGuinea have only three species peculiar to each, and Timor has five. Weshall have to look, not to single islands, but to whole groups, in orderto obtain an amount of individuality comparable with that of Celebes. For example, the extensive group comprising the large islands of Java, Borneo, and Sumatra, with the peninsula of Malacca, possessingaltogether 48 species, has about 24, or just half, peculiar to it; thenumerous group of the Philippines possess 22 species, of which 17 arepeculiar; the seven chief islands of the Moluccas have 27, of which 12are peculiar; and the whole of the Papuan Islands, with an equal numberof species, have 17 peculiar. Comparable with the most isolated of thesegroups is Celebes, with its 24 species, of which the large proportion of18 are peculiar. We see, therefore, that the opinion I have elsewhereexpressed, of the high degree of isolation and the remarkabledistinctive features of this interesting island, is fully borne out bythe examination of this conspicuous family of insects. A singlestraggling island with a few small satellites, it is zoologically ofequal importance with extensive groups of islands many times as largeas itself; and standing in the very centre of the archipelago, surrounded on every side with islets connecting it with the largergroups, and which seem to afford the greatest facilities for themigration and intercommunication of their respective productions, it yetstands out conspicuous with a character of its own in every departmentof nature, and presents peculiarities which are, I believe, without aparallel in any similar locality on the globe. Briefly to summarize these peculiarities, Celebes possesses three generaof mammals (out of the very small number which inhabit it) which are ofsingular and isolated forms, viz. , Cynopithecus, a tailless Ape alliedto the Baboons; Anoa, a straight-horned Antelope of obscure affinities, but quite unlike anything else in the whole archipelago or in India: andBabirusa, an altogether abnormal wild Pig. With a rather limited birdpopulation, Celebes has an immense preponderance of species confined toit, and has also six remarkable genera (Meropogon, Ceycopsis, Streptocitta, Enodes, Scissirostrum, and Megacephalon) entirelyrestricted to its narrow limits, as well as two others (Prioniturus andBasilornis) which only range to a single island beyond it. Mr. Smith's elaborate tables of the distribution of Malayan Hymenoptera(see "Proc. Linn. Soc. " Zool. Vol. Vii. ) show that out of the largenumber of 301 species collected in Celebes, 190 (or nearly two-thirds)are absolutely restricted to it, although Borneo on one side, and thevarious islands of the Moluccas on the other, were equally well exploredby me; and no less than twelve of the genera are not found in any otherisland of the archipelago. I have shown in the present essay that, inthe Papilionidæ, it has far more species of its own than any otherisland, and a greater proportion of peculiar species than many of thelarge groups of islands in the archipelago--and that it gives to a largenumber of the species and varieties which inhabit it, 1st, an increaseof size, and, 2nd, a peculiar modification in the form of the wings, which stamp upon the most dissimilar insects a mark distinctive of theircommon birth-place. What, I would ask, are we to do with phenomena such as these? Are we torest content with that very simple, but at the same time veryunsatisfying explanation, that all these insects and other animals werecreated exactly _as_ they are, and originally placed exactly _where_they are, by the inscrutable will of their Creator, and that we havenothing to do but to register the facts and wonder? Was this singleisland selected for a fantastic display of creative power, merely toexcite a childlike and unreasoning admiration? Is all this appearance ofgradual modification by the action of natural causes--a modification thesuccessive steps of which we can almost trace--all delusive? Is thisharmony between the most diverse groups, all presenting analogousphenomena, and indicating a dependence upon physical changes of which wehave independent evidence, all false testimony? If I could think so, thestudy of nature would have lost for me its greatest charm. I shouldfeel as would the geologist, if you could convince him that hisinterpretation of the earth's past history was all a delusion--thatstrata were never formed in the primeval ocean, and that the fossils heso carefully collects and studies are no true record of a former livingworld, but were all created just as they now are, and in the rocks wherehe now finds them. I must here express my own belief that none of these phenomena, howeverapparently isolated or insignificant, can ever stand alone--that not thewing of a butterfly can change in form or vary in colour, except inharmony with, and as a part of the grand march of nature. I believe, therefore, that all the curious phenomena I have just recapitulated, areimmediately dependent on the last series of changes, organic andinorganic, in these regions; and as the phenomena presented by theisland of Celebes differ from those of all the surrounding islands, itcan, I conceive, only be because the past history of Celebes has been, to some extent, unique and different from theirs. We must have much moreevidence to determine exactly in what that difference has consisted. Atpresent, I only see my way clear to one deduction, viz. , that Celebesrepresents one of the oldest parts of the archipelago; that it has beenformerly more completely isolated both from India and from Australiathan it is now, and that amid all the mutations it has undergone, arelic or substratum of the fauna and flora of some more ancient land hasbeen here preserved to us. It is only since my return home, and since I have been able to comparethe productions of Celebes side by side with those of the surroundingislands, that I have been fully impressed with their peculiarity, andthe great interest that attaches to them. The plants and the reptilesare still almost unknown; and it is to be hoped that some enterprisingnaturalist may soon devote himself to their study. The geology of thecountry would also be well worth exploring, and its newer fossils wouldbe of especial interest as elucidating the changes which have led to itspresent anomalous condition. This island stands, as it were, upon theboundary-line between two worlds. On one side is that ancient Australianfauna, which preserves to the present day the facies of an earlygeological epoch; on the other is the rich and varied fauna of Asia, which seems to contain, in every class and order, the most perfect andhighly organised animals. Celebes has relations to both, yet strictlybelongs to neither: it possesses characteristics which are altogetherits own; and I am convinced that no single island upon the globe wouldso well repay a careful and detailed research into its past and presenthistory. _Concluding Remarks. _ In writing this essay it has been my object to show how much may, underfavourable circumstances, be learnt by the study of what may be termedthe external physiology of a small group of animals, inhabiting alimited district. This branch of natural history had received littleattention till Mr. Darwin showed how important an adjunct it may becometowards a true interpretation of the history of organized beings, andattracted towards it some small share of that research which had beforebeen almost exclusively devoted to internal structure and physiology. The nature of species, the laws of variation, the mysterious influenceof locality on both form and colour, the phenomena of dimorphism and ofmimicry, the modifying influence of sex, the general laws ofgeographical distribution, and the interpretation of past changes of theearth's surface, have all been more or less fully illustrated by thevery limited group of the Malayan Papilionidæ; while, at the same time, the deductions drawn therefrom have been shown to be supported byanalogous facts, occurring in other and often widely-separated groups ofanimals. V. ON INSTINCT IN MAN AND ANIMALS. The most perfect and most striking examples of what is termed instinct, those in which reason or observation appear to have the least influence, and which seem to imply the possession of faculties farthest removedfrom our own, are to be found among insects. The marvellous constructivepowers of bees and wasps, the social economy of ants, the carefulprovision for the safety of a progeny they are never to see manifestedby many beetles and flies, and the curious preparations for the pupastate by the larvæ of butterflies and moths, are typical examples ofthis faculty, and are supposed to be conclusive as to the existence ofsome power or intelligence, very different from that which we derivefrom our senses or from our reason. _How Instinct may be best Studied. _ Whatever we may define instinct to be, it is evidently some form ofmental manifestation, and as we can only judge of mind by the analogy ofour own mental functions and by observation of the results of mentalaction in other men and in animals, it is incumbent on us, first, tostudy and endeavour to comprehend the minds of infants, of savage men, and of animals not very far removed from ourselves, before we pronouncepositively as to the nature of the mental operations in creatures soradically different from us as insects. We have not yet even been ableto ascertain what are the senses they possess, or what relation theirpowers of seeing, hearing, and feeling have to ours. Their sight may farexceed ours both in delicacy and in range, and may possibly give themknowledge of the internal constitution of bodies analogous to that whichwe obtain by the spectroscope; and that their visual organs do possesssome powers which ours do not, is indicated by the extraordinarycrystalline rods radiating from the optic ganglion to the facets of thecompound eye, which rods vary in form and thickness in different partsof their length, and possess distinctive characters in each group ofinsects. This complex apparatus, so different from anything in the eyesof vertebrates, may subserve some function quite inconceivable by us, aswell as that which we know as vision. There is reason to believe thatinsects appreciate sounds of extreme delicacy, and it is supposed thatcertain minute organs, plentifully supplied with nerves, and situated inthe subcostal vein of the wing in most insects, are the organs ofhearing. But besides these, the Orthoptera (such as grasshoppers, &c. )have what are supposed to be ears on their fore legs, and Mr. Lownebelieves that the little stalked balls, which are the sole remnants ofthe hind wings in flies, are also organs of hearing or of some analogoussense. In flies, too, the third joint of the antennæ contains thousandsof nerve-fibres, which terminate in small open cells, and this Mr. Lownebelieves to be the organ of smell, or of some other, perhaps new, sense. It is quite evident, therefore, that insects may possess senses whichgive them a knowledge of that which we can never perceive, and enablethem to perform acts which to us are incomprehensible. In the midst ofthis complete ignorance of their faculties and inner nature, is it wisefor us to judge so boldly of their powers by a comparison with our own?How can we pretend to fathom the profound mystery of their mentalnature, and decide what, and how much, they can perceive or remember, reason or reflect! To leap at one bound from our own consciousness tothat of an insect's, is as unreasonable and absurd as if, with a prettygood knowledge of the multiplication table, we were to go straight tothe study of the calculus of functions, or as if our comparativeanatomists should pass from the study of man's bony structure to that ofthe fish, and, without any knowledge of the numerous intermediate forms, were to attempt to determine the homologies between these distant typesof vertebrata. In such a case would not error be inevitable, and wouldnot continued study in the same direction only render the erroneousconclusions more ingrained and more irremovable. _Definition of Instinct. _ Before going further into this subject, we must determine what we meanby the term instinct. It has been variously defined as--"dispositionoperating without the aid of instruction or experience, " "a mental powertotally independent of organization, " or "a power enabling an animal todo that which, in those things man can do, results from a chain ofreasoning, and in things which man cannot do, is not to be explained byany efforts of the intellectual faculties. " We find, too, that the wordinstinct is very frequently applied to acts which are evidently theresult either of organization or of habit. The colt or calf is said towalk instinctively, almost as soon as it is born; but this is solely dueto its organization, which renders walking both possible and pleasurableto it. So we are said instinctively to hold out our hands to saveourselves from falling, but this is an acquired habit, which the infantdoes not possess. It appears to me that instinct should be definedas--"the performance by an animal of complex acts, absolutely withoutinstruction or previously-acquired knowledge. " Thus, acts are said to beperformed by birds in building their nests, by bees in constructingtheir cells, and by many insects in providing for the future wants ofthemselves or their progeny, without ever having seen such actsperformed by others, and without any knowledge of why they perform themthemselves. This is expressed by the very common term "blind instinct. "But we have here a number of assertions of matters of fact, which, strange to say, have never been proved to be facts at all. They arethought to be so self-evident that they may be taken for granted. Noone has ever yet obtained the eggs of some bird which builds anelaborate nest, hatched these eggs by steam or under a quite distinctparent, placed them afterwards in an extensive aviary or covered garden, where the situation and the materials of a nest similar to that of theparent birds may be found, and then seen what kind of nest these birdswould build. If under these rigorous conditions they choose the samematerials, the same situation, and construct the nest in the same wayand as perfectly as their parents did, instinct would be proved in theircase; now it is only assumed, and assumed, as I shall show further on, without any sufficient reason. So, no one has ever carefully taken thepupæ of a hive of bees out of the comb, removed them from the presenceof other bees, and loosed them in a large conservatory with plenty offlowers and food, and observed what kind of cells they would construct. But till this is done, no one can say that bees build withoutinstruction, no one can say that with every new swarm there are no beesolder than those of the same year, who may be the teachers in formingthe new comb. Now, in a scientific inquiry, a point which can be provedshould not be assumed, and a totally unknown power should not be broughtin to explain facts, when known powers may be sufficient. For both thesereasons I decline to accept the theory of instinct in any case where allother possible modes of explanation have not been exhausted. _Does Man possess Instincts. _ Many of the upholders of the instinctive theory maintain, that man hasinstincts exactly of the same nature as those of animals, but more orless liable to be obscured by his reasoning powers; and as this is acase more open to our observation than any other, I will devote a fewpages to its consideration. Infants are said to suck by instinct, andafterwards to walk by the same power, while in adult man the mostprominent case of instinct is supposed to be, the powers possessed bysavage races to find their way across a trackless and previously unknownwilderness. Let us take first the case of the infant's sucking. It issometimes absurdly stated that the new-born infant "seeks the breast, "and this is held to be a wonderful proof of instinct. No doubt it wouldbe if true, but unfortunately for the theory it is totally false, asevery nurse and medical man can testify. Still, the child undoubtedlysucks without teaching, but this is one of those _simple_ acts dependentupon organization, which cannot properly be termed instinct, any morethan breathing or muscular motion. Any object of suitable size in themouth of an infant excites the nerves and muscles so as to produce theact of suction, and when at a little later period, the will comes intoplay, the pleasurable sensations consequent on the act lead to itscontinuance. So, walking is evidently dependent on the arrangement ofthe bones and joints, and the pleasurable exertion of the muscles, whichlead to the vertical posture becoming gradually the most agreeable one;and there can be little doubt that an infant would learn of itself towalk, even if suckled by a wild beast. _How Indians travel through unknown and trackless Forests. _ Let us now consider the fact, of Indians finding their way throughforests they have never traversed before. This is much misunderstood, for I believe it is only performed under such special conditions, as atonce to show that instinct has nothing to do with it. A savage, it istrue, can find his way through his native forests in a direction inwhich he has never traversed them before; but this is because frominfancy he has been used to wander in them, and to find his way byindications which he has observed himself or learnt from others. Savagesmake long journeys in many directions, and, their whole faculties beingdirected to the subject, they gain a wide and accurate knowledge of thetopography, not only of their own district, but of all the regions roundabout. Every one who has travelled in a new direction communicates hisknowledge to those who have travelled less, and descriptions of routesand localities, and minute incidents of travel, form one of the mainstaples of conversation round the evening fire. Every wanderer orcaptive from another tribe adds to the store of information, and as thevery existence of individuals and of whole families and tribes, dependsupon the completeness of this knowledge, all the acute perceptivefaculties of the adult savage are devoted to acquiring and perfectingit. The good hunter or warrior thus comes to know the bearing of everyhill and mountain range, the directions and junctions of all thestreams, the situation of each tract characterized by peculiarvegetation, not only within the area he has himself traversed, but forperhaps a hundred miles around it. His acute observation enables him todetect the slightest undulations of the surface, the various changes ofsubsoil and alterations in the character of the vegetation, that wouldbe quite imperceptible to a stranger. His eye is always open to thedirection in which he is going; the mossy side of trees, the presence ofcertain plants under the shade of rocks, the morning and evening flightof birds, are to him indications of direction, almost as sure as the sunin the heavens. Now, if such a savage is required to find his way acrossthis country in a direction in which he has never been before, he isquite equal to the task. By however circuitous a route he has come tothe point he is to start from, he has observed all the bearings anddistances so well, that he knows pretty nearly where he is, thedirection of his own home and that of the place he is required to go to. He starts towards it, and knows that by a certain time he must cross anupland or a river, that the streams should flow in a certain direction, and that he should cross some of them at a certain distance from theirsources. The nature of the soil throughout the whole region is known tohim, as well as all the great features of the vegetation. As heapproaches any tract of country he has been in or near before, manyminute indications guide him, but he observes them so cautiously thathis white companions cannot perceive by what he has directed his course. Every now and then he slightly changes his direction, but he is neverconfused, never loses himself, for he always feels at home; till at lasthe arrives at a well-known country, and directs his course so as toreach the exact spot desired. To the Europeans whom he guides, he seemsto have come without trouble, without any special observation, and in anearly straight unchanging course. They are astonished, and ask if hehas ever been the same route before, and when he answers "No, " concludethat some unerring instinct could alone have guided him. But take thissame man into another country very similar to his own, but with otherstreams and hills, another kind of soil, with a somewhat differentvegetation and animal life; and after bringing him by a circuitous routeto a given point, ask him to return to his starting place, by a straightline of fifty miles through the forest, and he will certainly decline toattempt it, or, attempting it, will more or less completely fail. Hissupposed instinct does not act out of his own country. A savage, even in a new country, has, however, undoubted advantages, from his familiarity with forest life, his entire fearlessness of beinglost, his accurate perception of direction and of distance, and he isthus able very soon to acquire a knowledge of the district that seemsmarvellous to a civilized man; but my own observation of savages inforest countries has convinced me, that they find their way by the useof no other faculties than those which we ourselves possess. It appearsto me, therefore, that to call in the aid of a new and mysterious powerto account for savages being able to do that which, under similarconditions, we could almost all of us perform, although perhaps lessperfectly, is almost ludicrously unnecessary. In the next essay I shall attempt to show, that much of what has beenattributed to instinct in birds, can be also very well explained bycrediting them with those faculties of observation, memory, andimitation, and with that limited amount of reason, which theyundoubtedly exhibit. VI. THE PHILOSOPHY OF BIRDS' NESTS. _Instinct or Reason in the Construction of Birds' Nests. _ Birds, we are told, build their nests by _instinct_, while manconstructs his dwelling by the exercise of _reason_. Birds never change, but continue to build for ever on the self-same plan; man alters andimproves his houses continually. Reason advances; instinct isstationary. This doctrine is so very general that it may almost be said to beuniversally adopted. Men who agree on nothing else, accept this as agood explanation of the facts. Philosophers and poets, metaphysiciansand divines, naturalists and the general public, not only agree inbelieving this to be probable, but even adopt it as a sort of axiom thatis so self-evident as to need no proof, and use it as the veryfoundation of their speculations on instinct and reason. A belief sogeneral, one would think, must rest on indisputable facts, and be alogical deduction from them. Yet I have come to the conclusion that notonly is it very doubtful, but absolutely erroneous; that it not onlydeviates widely from the truth, but is in almost every particularexactly opposed to it. I believe, in short, that birds do _not_ buildtheir nests by instinct; that man does _not_ construct his dwelling byreason; that birds do change and improve when affected by the samecauses that make men do so; and that mankind neither alter nor improvewhen they exist under conditions similar to those which are almostuniversal among birds. _Do Men build by Reason or by Imitation?_ Let us first consider the theory of reason, as alone determining thedomestic architecture of the human race. Man, as a reasonable animal, itis said, continually alters and improves his dwelling. This I entirelydeny. As a rule, he neither alters nor improves, any more than the birdsdo. What have the houses of most savage tribes improved from, each asinvariable as the nest of a species of bird? The tents of the Arab arethe same now as they were two or three thousand years ago, and the mudvillages of Egypt can scarcely have improved since the time of thePharaohs. The palm-leaf huts and hovels of the various tribes of SouthAmerica and the Malay Archipelago, what have they improved from sincethose regions were first inhabited? The Patagonian's rude shelter ofleaves, the hollowed bank of the South African Earthmen, we cannot evenconceive to have been ever inferior to what they now are. Even nearerhome, the Irish turf cabin and the Highland stone shelty can hardly haveadvanced much during the last two thousand years. Now, no one imputesthis stationary condition of domestic architecture among these savagetribes to instinct, but to simple imitation from one generation toanother, and the absence of any sufficiently powerful stimulus tochange or improvement. No one imagines that if an infant Arab could betransferred to Patagonia, or to the Highlands, it would, when it grewup, astonish its foster-parents by constructing a tent of skins. On theother hand, it is quite clear that physical conditions, combined withthe degree of civilization arrived at, almost necessitate certain typesof structure. The turf, or stones, or snow--the palm-leaves, bamboo, orbranches, which are the materials of houses in various countries, areused because nothing else is so readily to be obtained. The Egyptianpeasant has none of these, not even wood. What, then, can he use butmud? In tropical forest-countries, the bamboo and the broad palm-leavesare the natural material for houses, and the form and mode of structurewill be decided in part by the nature of the country, whether hot orcool, whether swampy or dry, whether rocky or plain, whether frequentedby wild beasts, or whether subject to the attacks of enemies. When oncea particular mode of building has been adopted, and has become confirmedby habit and by hereditary custom, it will be long retained, even whenits utility has been lost through changed conditions, or throughmigration into a very different region. As a general rule, throughoutthe whole continent of America, native houses are built directly uponthe ground--strength and security being given by thickening the lowwalls and the roof. In almost the whole of the Malay Islands, on thecontrary, the houses are raised on posts, often to a great height, withan open bamboo floor; and the whole structure is exceedingly slight andthin. Now, what can be the reason of this remarkable difference betweencountries, many parts of which are strikingly similar in physicalconditions, natural productions, and the state of civilization of theirinhabitants? We appear to have some clue to it in the supposed originand migrations of their respective populations. The indigenes oftropical America are believed to have immigrated from the north--from acountry where the winters are severe, and raised houses with open floorswould be hardly habitable. They moved southwards by land along themountain ranges and uplands, and in an altered climate continued themode of construction of their forefathers, modified only by the newmaterials they met with. By minute observations of the Indians of theAmazon Valley, Mr. Bates arrived at the conclusion that they werecomparatively recent immigrants from a colder climate. He says:--"No onecould live long among the Indians of the Upper Amazon without beingstruck with their constitutional dislike to the heat ... Their skin ishot to the touch, and they perspire little ... They are restless anddiscontented in hot, dry weather, but cheerful on cool days, when therain is pouring down their naked backs. " And, after giving many otherdetails, he concludes, "How different all this is with the Negro, thetrue child of tropical climes! The impression gradually forced itself onmy mind that the Red Indian lives as an immigrant or stranger in thesehot regions, and that his constitution was not originally adapted, andhas not since become perfectly adapted, to the climate. " The Malay races, on the other hand, are no doubt very ancientinhabitants of the hottest regions, and are particularly addicted toforming their first settlements at the mouths of rivers or creeks, or inland-locked bays and inlets. They are a pre-eminently maritime orsemi-aquatic people, to whom a canoe is a necessary of life, and whowill never travel by land if they can do so by water. In accordance withthese tastes, they have built their houses on posts in the water, afterthe manner of the lake-dwellers of ancient Europe; and this mode ofconstruction has become so confirmed, that even those tribes who havespread far into the interior, on dry plains and rocky mountains, continue to build in exactly the same manner, and find safety in theheight to which they elevate their dwellings above the ground. _Why does each Bird build a peculiar kind of Nest?_ These general characteristics of the abode of savage man will be foundto be exactly paralleled by the nests of birds. Each species uses thematerials it can most readily obtain, and builds in situations mostcongenial to its habits. The wren, for example, frequenting hedgerowsand low thickets, builds its nest generally of _moss_, a material alwaysfound where it lives, and among which it probably obtains much of itsinsect food; but it varies sometimes, using hay or feathers when theseare at hand. Rooks dig in pastures and ploughed fields for grubs, andin doing so must continually encounter _roots_ and _fibres_. These areused to line its nest. What more natural! The crow feeding on carrion, dead rabbits, and lambs, and frequenting sheep-walks and warrens, chooses _fur_ and _wool_ to line its nest. The lark frequents cultivatedfields, and makes its nest, on the ground, of grass lined with_horsehair_--materials the most easy to meet with, and the best adaptedto its needs. The kingfisher makes its nest of the _bones_ of the fishwhich it has eaten. Swallows use clay and mud from the margins of theponds and rivers over which they find their insect food. The materialsof birds' nests, like those used by savage man for his house, are, then, those which come first to hand; and it certainly requires no morespecial instinct to select them in one case than in the other. But, it will be said, it is not so much the materials as the form andstructure of nests, that vary so much, and are so wonderfully adapted tothe wants and habits of each species; how are these to be accounted forexcept by instinct? I reply, they may be in a great measure explained bythe general habits of the species, the nature of the tools they have towork with, and the materials they can most easily obtain, with the verysimplest adaptations of means to an end, quite within the mentalcapacities of birds. The delicacy and perfection of the nest will bear adirect relation to the size of the bird, its structure and habits. Thatof the wren or the humming-bird is perhaps not finer or more beautifulin proportion than that of the blackbird, the magpie, or the crow. Thewren, having a slender beak, long legs, and great activity, is able withgreat ease to form a well-woven nest of the finest materials, and placesit in thickets and hedgerows which it frequents in its search for food. The titmouse, haunting fruit-trees and walls, and searching in cracksand crannies for insects, is naturally led to build in holes where ithas shelter and security; while its great activity, and the perfectionof its tools (bill and feet), enable it readily to form a beautifulreceptacle for its eggs and young. Pigeons having heavy bodies and weakfeet and bills (imperfect tools for forming a delicate structure) buildrude, flat nests of sticks, laid across strong branches which will beartheir weight and that of their bulky young. They can do no better. TheCaprimulgidæ have the most imperfect tools of all, feet that will notsupport them except on a flat surface (for they cannot truly perch) anda bill excessively broad, short, and weak, and almost hidden by feathersand bristles. They cannot build a nest of twigs or fibres, hair or moss, like other birds, and they therefore generally dispense with onealtogether, laying their eggs on the bare ground, or on the stump orflat limb of a tree. The clumsy hooked bills, short necks and feet, andheavy bodies of Parrots, render them quite incapable of building a nestlike most other birds. They cannot climb up a branch without using bothbill and feet; they cannot even turn round on a perch without holding onwith their bill. How, then, could they inlay, or weave, or twist thematerials of a nest? Consequently, they all lay in holes of trees, thetops of rotten stumps, or in deserted ants' nests, the soft materials ofwhich they can easily hollow out. Many terns and sandpipers lay their eggs on the bare sand of thesea-shore, and no doubt the Duke of Argyll is correct when he says, thatthe cause of this habit is not that they are unable to form a nest, butthat, in such situations, any nest would be conspicuous and lead to thediscovery of the eggs. The choice of _place_ is, however, evidentlydetermined by the habits of the birds, who, in their daily search forfood, are continually roaming over extensive tide-washed flats. Gullsvary considerably in their mode of nesting, but it is always inaccordance with their structure and habits. The situation is either on abare rock or on ledges of sea-cliffs, in marshes or on weedy shores. Thematerials are sea-weed, tufts of grass or rushes, or the _débris_ of theshore, heaped together with as little order and constructive art asmight be expected from the webbed feet and clumsy bill of these birds, the latter better adapted for seizing fish than for forming a delicatenest. The long-legged, broad-billed flamingo, who is continuallystalking over muddy flats in search of food, heaps up the mud into aconical stool, on the top of which it lays its eggs. The bird can thussit upon them conveniently, and they are kept dry, out of reach of thetides. Now I believe that throughout the whole class of birds the same generalprinciples will be found to hold good, sometimes distinctly, sometimesmore obscurely apparent, according as the habits of the species are moremarked, or their structure more peculiar. It is true that, among birdsdiffering but little in structure or habits, we see considerablediversity in the mode of nesting, but we are now so well assured thatimportant changes of climate and of surface have occurred within theperiod of existing species, that it is by no means difficult to see howsuch differences have arisen. Simple habits are known to be hereditary, and as the area now occupied by each species is different from that ofevery other, we may be sure that such changes would act differently uponeach, and would often bring together species which had acquired theirpeculiar habits in distinct regions and under different conditions. _How do Young Birds learn to Build their First Nest?_ But it is objected, birds do not _learn_ to make their nest as man doesto build, for all birds will make exactly the same nest as the rest oftheir species, even if they have never seen one, and it is instinctalone that can enable them to do this. No doubt this would be instinctif it were true, and I simply ask for proof of the fact. This point, although so important to the question at issue, is always assumedwithout proof, and even against proof, for what facts there are, areopposed to it. Birds brought up from the egg in cages do not make thecharacteristic nest of their species, even though the proper materialsare supplied them, and often make no nest at all, but rudely heaptogether a quantity of materials; and the experiment has never beenfairly tried, of turning out a pair of birds so brought up, into anenclosure covered with netting, and watching the result of theiruntaught attempts at nest-making. With regard to the songs of birds, however, which is thought to be equally instinctive, the experiment hasbeen tried, and it is found that young birds never have the songpeculiar to their species if they have not heard it, whereas theyacquire very easily the song of almost any other bird with which theyare associated. _Do Birds sing by Instinct or by Imitation?_ The Hon. Daines Barrington was of opinion that "notes in birds are nomore innate than language is in man, and depend entirely on the masterunder which they are bred, _as far as their organs will enable them toimitate_ the sounds which they have frequent opportunities of hearing. "He has given an account of his experiments in the "PhilosophicalTransactions" for 1773 (Vol. 63); he says: "I have educated nestlinglinnets under the three best singing larks--the skylark, woodlark, andtitlark, every one of which, instead of the linnet's song, adheredentirely to that of their respective instructors. When the note of thetitlark linnet was thoroughly fixed, I hung the bird in a room with twocommon linnets for a quarter of a year, which were full in song; thetitlark linnet, however, did not borrow any passage from the linnet'ssong, but adhered stedfastly to that of the titlark. " He then goes onto say that birds taken from the nest at two or three weeks old havealready learnt the call-note of their species. To prevent this the birdsmust be taken from the nest when a day or two old, and he gives anaccount of a goldfinch which he saw at Knighton in Radnorshire, andwhich sang exactly like a wren, without any portion of the proper noteof its species. This bird had been taken from the nest at two or threedays old, and had been hung at a window opposite a small garden, whereit had undoubtedly acquired the notes of the wren without having anyopportunity of learning even the call of the goldfinch. He also saw a linnet, which had been taken from the nest when only twoor three days old, and which, not having any other sounds to imitate, had learnt almost to articulate, and could repeat the words "PrettyBoy, " and some other short sentences. Another linnet was educated by himself under a _vengolina_ (a smallAfrican finch, which he says sings better than any foreign bird but theAmerican mocking bird), and it imitated its African master so exactlythat it was impossible to distinguish the one from the other. Still more extraordinary was the case of a common house sparrow, whichonly chirps in a wild state, but which learnt the song of the linnet andgoldfinch by being brought up near those birds. The Rev. W. H. Herbert made similar observations, and states that theyoung whinchat and wheatear, which have naturally little variety ofsong, are ready in confinement to learn from other species, and becomemuch better songsters. The bullfinch, whose natural notes are weak, harsh, and insignificant, has nevertheless a wonderful musical faculty, since it can be taught to whistle complete tunes. The nightingale, onthe other hand, whose natural song is so beautiful, is exceedingly aptin confinement to learn that of other birds instead. Bechstein gives anaccount of a redstart which had built under the eaves of his house, which imitated the song of a caged chaffinch in a window underneath, while another in his neighbour's garden repeated some of the notes of ablackcap, which had a nest close by. These facts, and many others which might be quoted, render it certainthat the peculiar notes of birds are acquired by imitation, as surely asa child learns English or French, not by instinct, but by hearing thelanguage spoken by its parents. It is especially worthy of remark that, for young birds to acquire a newsong correctly, they must be taken out of hearing of their parents verysoon, for in the first three or four days they have already acquiredsome knowledge of the parent notes, which they will afterwards imitate. This shows that very young birds can both hear and remember, and itwould be very extraordinary if, after they could see, they could neitherobserve nor recollect, and could live for days and weeks in a nest andknow nothing of its materials and the manner of its construction. During the time they are learning to fly and return often to the nest, they must be able to examine it inside and out in every detail, and aswe have seen that their daily search for food invariably leads themamong the materials of which it is constructed, and among places similarto that in which it is placed, is it so very wonderful that when theywant one themselves they should make one like it? How else, in fact, should they make it? Would it not be much more remarkable if they wentout of their way to get materials quite different from those used in theparent nest, if they arranged them in a way they had seen no example of, and formed the whole structure differently from that in which theythemselves were reared, and which we may fairly presume is that whichtheir whole organization is best adapted to put together with celerityand ease? It has, however, been objected that observation, imitation, ormemory, can have nothing to do with a bird's architectural powers, because the young birds, which in England are born in May or June, willproceed in the following April or May to build a nest as perfect and asbeautiful as that in which it was hatched, although it could never haveseen one built. But surely the young birds _before_ they left the nesthad ample opportunities of observing its _form_, its _size_, its_position_, the _materials_ of which it was constructed, and the mannerin which those materials were arranged. Memory would retain theseobservations till the following spring, when the materials would come intheir way during their daily search for food, and it seems highlyprobable that the older birds would begin building first, and that thoseborn the preceding summer would follow their example, learning from themhow the foundations of the nest are laid and the materials puttogether. [H] +--------------------------------------------------------------+ | [H] It has been very pertinently remarked by a friend, that, | | if young birds did observe the nest they were reared in, | | they would consider it to be a natural production like the | | leaves and branches and matted twigs that surrounded it, and | | could not possibly conclude that their parents had | | constructed the one and not the other. This may be a valid | | objection, and, if so, we shall have to depend on the mode | | of instruction described in the succeeding paragraphs, but | | the question can only be finally decided by a careful set of | | experiments. | +--------------------------------------------------------------+ Again, we have no right to assume that young birds generally pairtogether. It seems probable that in each pair there is most frequentlyonly one bird born the preceding summer, who would be guided, to someextent, by its partner. My friend, Mr. Richard Spruce, the well-known traveller and botanist, thinks this is the case, and has kindly allowed me to publish thefollowing observations, which he sent me after reading my book. _How young Birds may learn to build Nests. _ "Among the Indians of Peru and Ecuador, many of whose customs are relicsof the semi-civilisation that prevailed before the Spanish conquest, itis usual for the young men to marry old women, and the young women oldmen. A young man, they say, accustomed to be tended by his mother, wouldfare ill if he had only an ignorant young girl to take care of him; andthe girl herself would be better off with a man of mature years, capableof supplying the place of a father to her. "Something like this custom prevails among many animals. A stout oldbuck can generally fight his way to the doe of his choice, and indeed ofas many does as he can manage; but a young buck 'of his first horns, 'must either content himself with celibacy, or with some damewell-stricken in years. "Compare the nearly parallel case of the domestic cock and of many otherbirds. Then consider the consequences amongst birds that pair, if an oldcock sorts with a young hen and an old hen with a young cock, as I thinkis certainly the case with blackbirds and others that are known to fightfor the youngest and handsomest females. One of each pair being alreadyan 'old bird, ' will be competent to instruct its younger partner (notonly in the futility of 'chaff, ' but) in the selection of a site for anest and how to build it; then, how eggs are hatched and young birdsreared. "Such, in brief, is my idea of how a bird on its first espousals may betaught the Whole Duty of the married state. " On this difficult point I have sought for information from some of ourbest field ornithologists, but without success, as it is in most casesimpossible to distinguish old from young birds after the first year. Iam informed, however, that the males of blackbirds, sparrows, and manyother kinds fight furiously, and the conqueror of course has the choiceof a mate. Mr. Spruce's view is at least as probable as the contrary one(that young birds, _as a rule_, pair together), and it is to some extentsupported by the celebrated American observer, Wilson, who stronglyinsists on the variety in the nests of birds of the same species, somebeing so much better finished than others; and he believes _that theless perfect nests are built by the younger, the more perfect by theolder, birds_. At all events, till the crucial experiment is made, and a pair of birdsraised from the egg without ever seeing a nest are shown to be capableof making one exactly of the parental type, I do not think we arejustified in calling in the aid of an unknown and mysterious faculty todo that which is so strictly analogous to the house-building of savageman. Again, we always assume that because a nest appears to us delicately andartfully built, that it therefore requires much special knowledge andacquired skill (or their substitute, instinct) in the bird who buildsit. We forget that it is formed twig by twig and fibre by fibre, rudelyenough at first, but crevices and irregularities, which must seem hugegaps and chasms in the eyes of the little builders, are filled up bytwigs and stalks pushed in by slender beak and active foot, and that thewool, feathers, or horsehair are laid thread by thread, so that theresult seems a marvel of ingenuity to us, just as would the rudestIinand hut to a native of Brobdignag. Levaillant has given an accountof the process of nest-building by a little African warbler, whichsufficiently shows that a very beautiful structure may be produced withvery little art. The foundation was laid of moss and flax interwovenwith grass and tufts of cotton, and presented a rude mass, five or sixinches in diameter, and four inches thick. This was pressed and trampleddown repeatedly, so as at last to make it into a kind of felt. The birdspressed it with their bodies, turning round upon them in everydirection, so as to get it quite firm and smooth before raising thesides. These were added bit by bit, trimmed and beaten with the wingsand feet, so as to felt the whole together, projecting fibres being nowand then worked in with the bill. By these simple and apparentlyinefficient means, the inner surface of the nest was rendered almost assmooth and compact as a piece of cloth. _Man's Works mainly Imitative. _ But look at civilised man! it is said; look at Grecian, and Egyptian, and Roman, and Gothic, and modern Architecture! What advance! whatimprovement! what refinements! This is what reason leads to, whereasbirds remain for ever stationary. If, however, such advances as theseare required, to prove the effects of reason as contrasted withinstinct, then all savage and many half-civilized tribes have no reason, but build instinctively quite as much as birds do. Man ranges over the whole earth, and exists under the most variedconditions, leading necessarily to equally varied habits. Hemigrates--he makes wars and conquests--one race mingles withanother--different customs are brought into contact--the habits of amigrating or conquering race are modified by the different circumstancesof a new country. The civilized race which conquered Egypt must havedeveloped its mode of building in a forest country where timber wasabundant, for it is not probable, that the idea of cylindrical columnsoriginated in a country destitute of trees. The pyramids might have beenbuilt by an indigenous race, but not the temples of El Uksor and Karnak. In Grecian architecture, almost every characteristic feature can betraced to an origin in wooden buildings. The columns, the architrave, the frieze, the fillets, the cantelevers, the form of the roof, allpoint to an origin in some southern forest-clad country, and strikinglycorroborate the view derived from philology, that Greece was colonisedfrom north-western India. But to erect columns and span them with hugeblocks of stone, or marble, is not an act of reason, but one of pureunreasoning imitation. The arch is the only true and reasonable mode ofcovering over wide spaces with stone, and therefore, Grecianarchitecture, however exquisitely beautiful, is false in principle, andis by no means a good example of the application of reason to the art ofbuilding. And what do most of us do at the present day but imitate thebuildings of those that have gone before us? We have not even been ableto discover or develope any definite style of building best suited forus. We have no characteristic national style of architecture, and tothat extent are even below the birds, who have each their characteristicform of nest, exactly adapted to their wants and habits. _Birds do Alter and Improve their Nests when altered Conditions requireit. _ The great uniformity in the architecture of each species of bird whichhas been supposed to prove a nest-building instinct, we may, therefore, fairly impute to the uniformity of the conditions under which eachspecies lives. Their range is often very limited, and they very seldompermanently change their country, so as to be placed in new conditions. When, however, new conditions do occur, they take advantage of them justas freely and wisely as man could do. The chimney and house-swallows area standing proof of a change of habit since chimneys and houses werebuilt, and in America this change has taken place within about threehundred years. Thread and worsted are now used in many nests instead ofwool and horsehair, and the jackdaw shows an affection for the churchsteeple which can hardly be explained by instinct. In the more thicklypopulated parts of the United States, the Baltimore oriole uses allsorts of pieces of string, skeins of silk, or the gardener's bass, toweave into its fine pensile nest, instead of the single hairs andvegetable fibres it has painfully to seek in wilder regions; and Wilson, a most careful observer, believes that it improves in nest-building bypractice--the older birds making the best nests. The purple martin takespossession of empty gourds or small boxes, stuck up for its reception inalmost every village and farm in America; and several of the Americanwrens will also build in cigar boxes, with a small hole cut in them, ifplaced in a suitable situation. The orchard oriole of the United Statesoffers us an excellent example of a bird which modifies its nestaccording to circumstances. When built among firm and stiff branches thenest is very shallow, but if, as is often the case, it is suspended fromthe slender twigs of the weeping willow, it is made much deeper, so thatwhen swayed about violently by the wind the young may not tumble out. Ithas been observed also, that the nests built in the warm Southern Statesare much slighter and more porous in texture than those in the colderregions of the north. Our own house-sparrow equally well adapts himselfto circumstances. When he builds in trees, as he, no doubt, always didoriginally, he constructs a well-made domed nest, perfectly fitted toprotect his young ones; but when he can find a convenient hole in abuilding or among thatch, or in any well-sheltered place, he takes muchless trouble, and forms a very loosely-built nest. A curious example of a recent change of habits has occurred in Jamaica. Previous to 1854, the palm swift (Tachornis phænicobea) inhabitedexclusively the palm trees in a few districts in the island. A colonythen established themselves in two cocoa-nut palms in Spanish Town, andremained there till 1857, when one tree was blown down, and the otherstripped of its foliage. Instead of now seeking out other palm trees, the swifts drove out the swallows who built in the Piazza of the Houseof Assembly, and took possession of it, building their nests on the topsof the end walls and at the angles formed by the beams and joists, aplace which they continue to occupy in considerable numbers. It isremarked that here they form their nest with much less elaboration thanwhen built in the palms, probably from being less exposed. A still more curious example of change and improvement in nest buildingwas published by Mr. F. A. Pouchet, in the tenth number of the _ComptesRendus_ for 1870, just as the first edition of this work appeared. Fortyyears ago M. Pouchet had himself collected nests of the House-Martin orWindow-Swallow (_Hirundo urbica_) from old buildings at Rouen, anddeposited them in the museum of that city. On recently obtaining somemore nests he was surprised, on comparing them with the old ones, tofind that they exhibited a decided change of form and structure. Thisled him to investigate the matter more closely. The changed nests hadbeen obtained from houses in a newly erected quarter of the city, and hefound that all the nests in the newly-built streets were of the newform. But on visiting the churches and older buildings, and some rockswhere these birds build, he found many nests of the old type along withsome of the new pattern. He then examined all the figures anddescriptions of the older naturalists, and found that they invariablyrepresented the older form only. The difference between the two forms he states to be as follows. In theold form the nest is a portion of a globe--when situated in the upperangle of a window one-fourth of a hemisphere--and the opening is verysmall and circular, being of a size just sufficient to allow the body ofthe bird to pass. In the new form the nest is much wider in proportionto its height, being a segment of a depressed spheroid, and the apertureis very wide and shallow, and close to the horizontal surface to whichthe nest is attached above. M. Pouchet thinks that the new form is an undoubted improvement on theold. The nest has a wider bottom and must allow the young ones to havemore freedom of motion than in the old narrower, and deeper nests, andits wide aperture allows the young birds to peep out and breathe thefresh air. This is so wide as to serve as a sort of balcony for them, and two young ones can often be seen on it without interfering with thepassage in and out of the old birds. At the same time, by being so closeto the roof, it is a better protection against rain, against cold, andagainst enemies, than the small round hole of the old nests. Here, then, we have an improvement in nest building, as well marked as anyimprovement that takes place in human dwellings in so short a time. But perfection of structure and adaptation to purpose, are not universalcharacteristics of birds' nests, since there are decided imperfectionsin the nesting of many birds which are quite compatible with our presenttheory, but are hardly so with that of instinct, which is supposed to beinfallible. The Passenger pigeon of America often crowds the brancheswith its nests till they break, and the ground is strewn with shatterednests, eggs, and young birds. Rooks' nests are often so imperfect thatduring high winds the eggs fall out; but the Window-Swallow is the mostunfortunate in this respect, for White, of Selborne, informs us that hehas seen them build, year after year, in places where their nests areliable to be washed away by a heavy rain and their young ones destroyed. _Conclusion. _ A fair consideration of all these facts will, I think, fully support thestatement with which I commenced, and show, that the mental facultiesexhibited by birds in the construction of their nests, are the same inkind as those manifested by mankind in the formation of their dwellings. These are, essentially, imitation, and a slow and partial adaptation tonew conditions. To compare the work of birds with the highestmanifestations of human art and science, is totally beside the question. I do not maintain that birds are gifted with reasoning faculties at allapproaching in variety and extent to those of man. I simply hold thatthe phenomena presented by their mode of building their nests, whenfairly compared with those exhibited by the great mass of mankind inbuilding their houses, indicate no essential difference in the kind ornature of the mental faculties employed. If instinct means anything, itmeans the capacity to perform some complex act without teaching orexperience. It implies innate ideas of a very definite kind, and, ifestablished, would overthrow Mr. Mill's sensationalism and all themodern philosophy of experience. That the existence of true instinct maybe established in other cases is not impossible, but in the particularinstance of birds' nests, which is usually considered one of itsstrongholds, I cannot find a particle of evidence to show the existenceof anything beyond those lower reasoning and imitative powers, whichanimals are universally admitted to possess. VII. A THEORY OF BIRDS' NESTS; SHOWING THE RELATION OF CERTAIN DIFFERENCES OF COLOUR IN FEMALEBIRDS, TO THEIR MODE OF NIDIFICATION. The habit of forming a more or less elaborate structure for thereception of their eggs and young, must undoubtedly be looked upon asone of the most remarkable and interesting characteristics of the classof birds. In other classes of vertebrate animals, such structures arefew and exceptional, and never attain to the same degree of completenessand beauty. Birds' nests have, accordingly, attracted much attention, and have furnished one of the stock arguments to prove the existence ofa blind but unerring instinct in the lower animals. The very generalbelief that every bird is enabled to build its nest, not by the ordinaryfaculties of observation, memory, and imitation, but by means of someinnate and mysterious impulse, has had the bad effect of withdrawingattention from the very evident relation that exists between thestructure, habits, and intelligence of birds, and the kind of nests theyconstruct. In the preceding essay I have detailed several of these relations, andthey teach us, that a consideration of the structure, the food, andother specialities of a bird's existence, will give a clue, andsometimes a very complete one, to the reason why it builds its nest ofcertain materials, in a definite situation, and in a more or lesselaborate manner. I now propose to consider the question from a more general point ofview, and to discuss its application to some important problems in thenatural history of birds. _Changed Conditions and persistent Habits as influencing Nidification. _ Besides the causes above alluded to, there are two other factors whoseeffect in any particular case we can only vaguely guess at, but whichmust have had an important influence in determining the existing detailsof nidification. These are--changed conditions of existence, whetherinternal or external, and the influence of hereditary or imitativehabit; the first inducing alterations in accordance with changes oforganic structure, of climate, or of the surrounding fauna and flora;the other preserving the peculiarities so produced, even when changedconditions render them no longer necessary. Many facts have been alreadygiven which show that birds do adapt their nests to the situations inwhich they place them, and the adoption of eaves, chimneys, and boxes, by swallows, wrens, and many other birds, shows that they are alwaysready to take advantage of changed conditions. It is probable, therefore, that a permanent change of climate would cause many birds tomodify the form or materials of their abodes, so as better to protecttheir young. The introduction of new enemies to eggs or young birds, might introduce many alterations tending to their better concealment. Achange in the vegetation of a country, would often necessitate the useof new materials. So, also, we may be sure, that as a species slowlybecame modified in any external or internal characters, it wouldnecessarily change in some degree its mode of building. This effectwould be produced by modifications of the most varied nature; such asthe power and rapidity of flight, which must often determine thedistance to which a bird will go to obtain materials for its nest; thecapacity of sustaining itself almost motionless in the air, which mustsometimes determine the position in which a nest can be built; thestrength and grasping power of the foot in relation to the weight of thebird, a power absolutely essential to the constructor of adelicately-woven and well-finished nest; the length and fineness of thebeak, which has to be used like a needle in building the best textilenests; the length and mobility of the neck, which is needful for thesame purpose; the possession of a salivary secretion like that used inthe nests of many of the swifts and swallows, as well as that of thesong-thrush--peculiarities of habits, which ultimately depend onstructure, and which often determine the material most frequently metwith or most easily to be obtained. Modifications in any of thesecharacters would necessarily lead, either to a change in the materialsof the nest, or in the mode of combining them in the finishedstructure, or in the form or position of that structure. During all these changes, however, certain specialities of nest-buildingwould continue, for a shorter or a longer time after the causes whichhad necessitated them had passed away. Such records of a vanished pastmeet us everywhere, even in man's works, notwithstanding his boastedreason. Not only are the main features of Greek architecture, merereproductions in stone of what were originally parts of a woodenbuilding, but our modern copyists of Gothic architecture often buildsolid buttresses capped with weighty pinnacles, to support a wooden roofwhich has no outward thrust to render them necessary; and even thinkthey ornament their buildings by adding sham spouts of carved stone, while modern waterpipes, stuck on without any attempt at harmony, do thereal duty. So, when railways superseded coaches, it was thoughtnecessary to build the first-class carriages to imitate a number ofcoach-bodies joined together; and the arm-loops for each passenger tohold on by, which were useful when bad roads made every journey asuccession of jolts and lurches, were continued on our smoothmacadamised mail-routes, and, still more absurdly, remain to this day inour railway carriages, the relic of a kind of locomotion we can nowhardly realize. Another good example is to be seen in our boots. Whenelastic sides came into fashion we had been so long used to fasten themwith buttons or laces, that a boot without either looked bare andunfinished, and accordingly the makers often put on a row of uselessbuttons or imitation laces, because habit rendered the appearance ofthem necessary to us. It is universally admitted that the habits ofchildren and of savages give us the best clue to the habits and mode ofthought of animals; and every one must have observed how children atfirst imitate the actions of their elders, without any regard to the useor applicability of the particular acts. So, in savages, many customspeculiar to each tribe are handed down from father to son merely by theforce of habit, and are continued long after the purpose which theyoriginally served has ceased to exist. With these and a hundred similarfacts everywhere around us, we may fairly impute much of what we cannotunderstand in the details of Bird-Architecture to an analogous cause. Ifwe do not do so, we must assume, either that birds are guided in everyaction by pure reason to a far greater extent than men are, or that aninfallible instinct leads them to the same result by a different road. The first theory has never, that I am aware of, been maintained by anyauthor, and I have already shown that the second, although constantlyassumed, has never been proved, and that a large body of facts isentirely opposed to it. One of my critics has, indeed, maintained that Iadmit "instinct" under the term "hereditary habit;" but the whole courseof my argument shows that I do not do so. Hereditary habit is, indeed, the same as instinct when the term is applied to some simple actiondependent upon a peculiarity of structure which is hereditary; as whenthe descendants of tumbler pigeons tumble, and the descendants of pouterpigeons pout. In the present case, however, I compare it strictly to thehereditary, or more properly, persistent or imitative, habits ofsavages, in building their houses as their fathers did. Imitation is alower faculty than invention. Children and savages imitate before theyoriginate; birds, as well as all other animals, do the same. The preceding observations are intended to show, that the exact mode ofnidification of each species of bird is probably the result of a varietyof causes, which have been continually inducing changes in accordancewith changed organic or physical conditions. The most important of thesecauses seem to be, in the first place, the structure of the species, and, in the second, its environment or conditions of existence. Now weknow, that every one of the characters or conditions included underthese two heads is variable. We have seen that, on the large scale, themain features of the nest built by each group of birds, bears a relationto the organic structure of that group, and we have, therefore, a rightto infer, that as structure varies, the nest will vary also in someparticular corresponding to the changes of structure. We have seen also, that birds change the position, the form, and the construction of theirnest, whenever the available materials or the available situations, varynaturally or have been altered by man; and we have, therefore, a rightto infer that similar changes have taken place, when, by a naturalprocess, external conditions have become in any way permanently altered. We must remember, however, that all these factors are very stable duringmany generations, and only change at a rate commensurate with those ofthe great physical features of the earth as revealed to us by geology;and we may, therefore, infer that the form and construction of nests, which we have shown to be dependent on them, are equally stable. If, therefore, we find less important and more easily modified charactersthan these, so correlated with peculiarities of nidification as toindicate that one is probably the cause of the other, we shall bejustified in concluding that these variable characters are dependent onthe mode of nidification, and not that the form of the nest has beendetermined by these variable characters. Such a correlation I am nowabout to point out. _Classification of Nests. _ For the purpose of this inquiry it is necessary to group nests into twogreat classes, without any regard to their most obvious differences orresemblances, but solely looking to the fact of whether the contents(eggs, young, or sitting bird) are hidden or exposed to view. In thefirst class we place all those in which the eggs and young arecompletely hidden, no matter whether this is effected by an elaboratecovered structure, or by depositing the eggs in some hollow tree orburrow underground. In the second, we group all in which the eggs, young, and sitting bird are exposed to view, no matter whether there isthe most beautifully formed nest, or none at all. Kingfishers, whichbuild almost invariably in holes in banks; Woodpeckers and Parrots, which build in hollow trees; the Icteridæ of America, which all makebeautiful covered and suspended nests; and our own Wren, which builds adomed nest, are examples of the former; while our Thrushes, Warblers, and Finches, as well as the Crowshrikes, Chatterers, and Tanagers of thetropics, together with all Raptorial birds and Pigeons, and a vastnumber of others in every part of the world, all adopt the latter modeof building. It will be seen that this division of birds according to theirnidification, bears little relation to the character of the nest itself. It is a functional not a structural classification. The most rude andthe most perfect specimens of bird-architecture are to be found in bothsections. It has, however, a certain relation to natural affinities, forlarge groups of birds, undoubtedly allied, fall into one or the otherdivision exclusively. The species of a genus or of a family are rarelydivided between the two primary classes, although they are frequentlydivided between the two very distinct modes of nidification that existin the first of them. All the Scansorial or climbing, and most of the Fissirostral orwide-gaped birds, for example, build concealed nests; and, in the lattergroup, the two families which build open nests, the Swifts and theGoat-suckers, are undoubtedly very widely separated from the otherfamilies with which they are associated in our classifications. TheTits vary much in their mode of nesting, some making open nestsconcealed in a hole, while others build domed or even pendulous coverednests, but they all come under the same class. Starlings vary in asimilar way. The talking Mynahs, like our own starlings, build in holes, the glossy starlings of the East (of the genus Calornis) form a hangingcovered nest, while the genus Sturnopastor builds in a hollow tree. Oneof the most striking cases in which one family of birds is dividedbetween the two classes, is that of the Finches; for while most of theEuropean species build exposed nests, many of the Australian finchesmake them dome-shaped. _Sexual differences of Colour in Birds. _ Turning now from the nests to the creatures who make them, let usconsider birds themselves from a somewhat unusual point of view, andform them into separate groups, according as both sexes, or the malesonly, are adorned with conspicuous colours. The sexual differences of colour and plumage in birds are veryremarkable, and have attracted much attention; and, in the case ofpolygamous birds, have been well explained by Mr. Darwin's principle ofsexual selection. We can, to a great extent, understand how malePheasants and Grouse have acquired their more brilliant plumage andgreater size, by the continual rivalry of the males both in strength andbeauty; but this theory does not throw any light on the causes whichhave made the female Toucan, Bee-eater, Parroquet, Macaw and Tit, inalmost every case as gay and brilliant as the male, while the gorgeousChatterers, Manakins, Tanagers, and Birds of Paradise, as well as ourown Blackbird, have mates so dull and inconspicuous that they can hardlybe recognised as belonging to the same species. _The Law which connects the Colours of Female Birds with the mode ofNidification. _ The above-stated anomaly can, however, now be explained by the influenceof the mode of nidification, since I find that, with but very fewexceptions, it is the rule--_that when both sexes are of strikingly gayand conspicuous colours, the nest is of the first class, or such as toconceal the sitting bird; while, whenever there is a striking contrastof colours, the male being gay and conspicuous, the female dull andobscure, the nest is open and the sitting bird exposed to view_. I willnow proceed to indicate the chief facts that support this statement, andwill afterwards explain the manner in which I conceive the relation hasbeen brought about. We will first consider those groups of birds in which the female isgaily or at least conspicuously coloured, and is in most cases exactlylike the male. 1. Kingfishers (Alcedinidæ). In some of the most brilliant species ofthis family the female exactly resembles the male; in others there is asexual difference, but it rarely tends to make the female lessconspicuous. In some, the female has a band across the breast, which iswanting in the male, as in the beautiful Halcyon diops of Ternate. Inothers the band is rufous in the female, as in several of the Americanspecies; while in Dacelo gaudichaudii, and others of the same genus, thetail of the female is rufous, while that of the male is blue. In mostkingfishers the nest is in a deep hole in the ground; in Tanysiptera itis said to be in a hole in the nests of termites, or sometimes increvices under overhanging rocks. 2. Motmots (Momotidæ). In these showy birds the sexes are exactly alike, and the nest in a hole under ground. 3. Puff-birds (Bucconidæ). These birds are often gaily coloured; somehave coral-red bills; the sexes are exactly alike, and the nest is in ahole in sloping ground. 4. Trogons (Trogonidæ). In these magnificent birds the females aregenerally less brightly coloured than the males, but are yet often gayand conspicuous. The nest is in a hole of a tree. 5. Hoopoes (Upupidæ). The barred plumage and long crests of these birdsrender them conspicuous. The sexes are exactly alike, and the nest is ina hollow tree. 6. Hornbills (Bucerotidæ). These large birds have enormous colouredbills, which are generally quite as well coloured and conspicuous in thefemales. Their nests are always in hollow trees, where the female isentirely concealed. 7. Barbets (Capitonidæ). These birds are all very gaily-coloured, and, what is remarkable, the most brilliant patches of colour are disposedabout the head and neck, and are very conspicuous. The sexes areexactly alike, and the nest is in a hole of a tree. 8. Toucans (Rhamphastidæ). These fine birds are coloured in the mostconspicuous parts of their body, especially on the large bill, and onthe upper and lower tail coverts, which are crimson, white, or yellow. The sexes are exactly alike, and they always build in a hollow tree. 9. Plaintain-eaters (Musophagidæ). Here again the head and bill are mostbrilliantly coloured in both sexes, and the nest is in a hole of a tree. 10. Ground cuckoos (Centropus). These birds are often of conspicuouscolours, and are alike in both sexes. They build a domed nest. 11. Woodpeckers (Picidæ). In this family the females often differ fromthe males, in having a yellow or white, instead of a crimson crest, butare almost as conspicuous. They all nest in holes in trees. 12. Parrots (Psittaci). In this great tribe, adorned with the mostbrilliant and varied colours, the rule is, that the sexes are preciselyalike, and this is the case in the most gorgeous families, the lories, the cockatoos, and the macaws; but in some there is a sexual differenceof colour to a slight extent. All build in holes, mostly in trees, butsometimes in the ground, or in white ants' nests. In the single case inwhich the nest is exposed, that of the Australian ground parrot, Pezoporus formosus, the bird has lost the gay colouring of its allies, and is clothed in sombre and completely protective tints of dusky greenand black. 13. Gapers (Eurylæmidæ). In these beautiful Eastern birds, somewhatallied to the American chatterers, the sexes are exactly alike, and areadorned with the most gay and conspicuous markings. The nest is a wovenstructure, _covered over_, and suspended from the extremities ofbranches over water. 14. Pardalotus (Ampelidæ). In these Australian birds the females differfrom the males, but are often very conspicuous, having brightly-spottedheads. Their nests are sometimes dome-shaped, sometimes in holes oftrees, or in burrows in the ground. 15. Tits (Paridæ). These little birds are always pretty, and many(especially among the Indian species) are very conspicuous. They alwayshave the sexes alike, a circumstance very unusual among the smallergaily-coloured birds of our own country. The nest is always covered overor concealed in a hole. 16. Nuthatches (Sitta). Often very pretty birds, the sexes alike, andthe nest in a hole. 17. ---- (Sittella). The female of these Australian nuthatches is oftenthe most conspicuous, being white-and black-marked. The nest is, according to Gould, "completely concealed among upright twigs connectedtogether. " 18. Creepers (Climacteris). In these Australian creepers the sexes arealike, or the female most conspicuous, and the nest is in a hole of atree. 19. Estrelda, Amadina. In these genera of Eastern and Australian finchesthe females, although more or less different from the males, are stillvery conspicuous having a red rump, or being white spotted. They differfrom most others of the family in building domed nests. 20. Certhiola. In these pretty little American creepers the sexes arealike, and they build a domed nest. 21. Mynahs (Sturnidæ). These showy Eastern starlings have the sexesexactly alike. They build in holes of trees. 22. Calornis (Sturnidæ). These brilliant metallic starlings have nosexual differences. They build a pensile covered nest. 23. Hangnests (Icteridæ). The red or yellow and black plumage of most ofthese birds is very conspicuous, and is exactly alike in both sexes. They are celebrated for their fine purse-shaped pensile nests. It will be seen that this list comprehends six important families ofFissirostres, four of Scansores, the Psittaci, and several genera, withthree entire families of Passeres, comprising about twelve hundredspecies, or about one-seventh of all known birds. * * * * * The cases in which, whenever the male is gaily coloured, the female ismuch less gay or quite inconspicuous, are exceedingly numerous, comprising, in fact, almost all the bright-coloured Passeres, exceptthose enumerated in the preceding class. The following are the mostremarkable:-- 1. Chatterers (Cotingidæ). These comprise some of the most gorgeousbirds in the world, vivid blues, rich purples, and bright reds, beingthe most characteristic colours. The females are always obscurelytinted, and are often of a greenish hue, not easily visible among thefoliage. 2. Manakins (Pipridæ). These elegant birds, whose caps or crests are ofthe most brilliant colours, are usually of a sombre green in the femalesex. 3. Tanagers (Tanagridæ). These rival the chatterers in the brilliancy oftheir colours, and are even more varied. The females are generally ofplain and sombre hues, and always less conspicuous than the males. In the extensive families of the warblers (Sylviadæ), thrushes(Turdidæ), flycatchers (Muscicapidæ), and shrikes (Laniadæ), aconsiderable proportion of the species are beautifully marked with gayand conspicuous tints, as is also the case in the Pheasants and Grouse;but in every case the females are less gay, and are most frequently ofthe very plainest and least conspicuous hues. Now, throughout _the wholeof these families the nest is open_, and I am not aware of a singleinstance in which any one of these birds builds a _domed nest_, orplaces it in a _hole of a tree_, or _underground_, or in any place whereit is effectually concealed. In considering the question we are now investigating, it is notnecessary to take into account the larger and more powerful birds, because these seldom depend much on concealment to secure their safety. In the raptorial birds bright colours are as a rule absent; and theirstructure and habits are such as not to require any special protectionfor the female. The larger waders are sometimes very brightly colouredin both sexes; but they are probably little subject to the attacks ofenemies, since the scarlet ibis, the most conspicuous of birds, existsin immense quantities in South America. In game birds and water-fowl, however, the females are often very plainly coloured, when the males areadorned with brilliant hues; and the abnormal family of the Megapodidæoffers us the interesting fact of an identity in the colours of thesexes (which in Megacephalon and Talegalla are somewhat conspicuous), inconjunction with the habit of not sitting on the eggs at all. _What the Facts Teach us. _ Taking the whole body of evidence here brought forward, embracing as itdoes almost every group of bright-coloured birds, it will, I think, beadmitted that the relation between the two series of facts in thecolouring and nidification of birds has been sufficiently established. There are, it is true, a few apparent and some real exceptions, which Ishall consider presently; but they are too few and unimportant to weighmuch against the mass of evidence on the other side, and may for thepresent be neglected. Let us then consider what we are to do with thisunexpected set of correspondences between groups of phenomena which, atfirst sight, appear so disconnected. Do they fall in with any othergroups of natural phenomena? Do they teach us anything of the way inwhich nature works, and give us any insight into the causes which havebrought about the marvellous variety, and beauty, and harmony of livingthings? I believe we can answer these questions in the affirmative; andI may mention, as a sufficient proof that these are not isolated facts, that I was first led to see their relation to each other by the study ofan analogous though distinct set of phenomena among insects, that ofprotective resemblance and "mimicry. " On considering this remarkable series of corresponding facts, the firstthing we are taught by them seems to be, that there is no incapacity inthe female sex among birds, to receive the same bright hues and stronglycontrasted tints with which their partners are so often decorated, sincewhenever they are _protected and concealed_ during the period ofincubation _they are similarly adorned_. The fair inference is, that itis chiefly due to the absence of protection or concealment during thisimportant epoch, that gay and conspicuous tints are withheld or leftundeveloped. The mode in which this has been effected is veryintelligible, if we admit the action of natural and sexual selection. Itwould appear from the numerous cases in which both sexes are adornedwith equally brilliant colours (while both sexes are rarely armed withequally developed offensive and defensive weapons when not required forindividual safety), that the normal action of "sexual selection" is todevelop colour and beauty in both sexes, by the preservation andmultiplication of all varieties of colour in either sex which arepleasing to the other. Several very close observers of the habits ofanimals have assured me, that male birds and quadrupeds do often takevery strong likes and dislikes to individual females, and we can hardlybelieve that the one sex (the female) can have a general taste forcolour while the other has no such taste. However this may be, the factremains, that in a vast number of cases the female acquires as brilliantand as varied colours as the male, and therefore most probably acquiresthem in the same way as the male does; that is, either because thecolour is useful to it, or is correlated with some useful variation, oris pleasing to the other sex. The only remaining supposition is that itis transmitted from the other sex, without being of any use. From thenumber of examples above adduced of bright colours in the female, thiswould imply that colour-characters acquired by one sex are generally(but not necessarily) transmitted to the other. If this be the case itwill, I think, enable us to explain the phenomena, even if we do notadmit that the male bird is ever influenced in the choice of a mate byher more gay or perfect plumage. The female bird, while sitting on her eggs in an uncovered nest, is muchexposed to the attacks of enemies, and any modification of colour whichrendered her more conspicuous would often lead to her destruction andthat of her offspring. All variations of colour in this direction in thefemale, would therefore sooner or later be eliminated, while suchmodifications as rendered her inconspicuous, by assimilating her tosurrounding objects, as the earth or the foliage, would, on the whole, survive the longest, and thus lead to the attainment of those brown orgreen and inconspicuous tints, which form the colouring (of the uppersurface at least), of the vast majority of female birds which sit uponopen nests. This does not imply, as some have thought, that all female birds wereonce as brilliant as the males. The change has been a very gradual one, generally dating from the origin of genera or of larger groups, butthere can be no doubt that the remote ancestry of birds having greatsexual differences of colour, were nearly or quite alike, sometimes(perhaps in most cases) more nearly resembling the female, butoccasionally perhaps being nearer what the male is now. The young birds(which usually resemble the females) will probably give some idea ofthis ancestral type, and it is well known that the young of alliedspecies and of different sexes are often undistinguishable. _Colour more variable than Structure or Habits, and therefore theCharacter which has generally been Modified. _ At the commencement of this essay, I have endeavoured to prove, that thecharacteristic differences and the essential features of birds' nests, are dependent on the structure of the species and upon the present andpast conditions of their existence. Both these factors are moreimportant and less variable than colour; and we must therefore concludethat in most cases the mode of nidification (dependent on structure andenvironment) has been the cause, and not the effect, of the similarityor differences of the sexes as regards colour. When the confirmed habitof a group of birds, was to build their nests in holes of trees like thetoucans, or in holes in the ground like the kingfishers, the protectionthe female thus obtained, during the important and dangerous time ofincubation, placed the two sexes on an equality as regards exposure toattack, and allowed "sexual selection, " or any other cause, to actunchecked in the development of gay colours and conspicuous markings inboth sexes. When, on the other hand (as in the Tanagers and Flycatchers), the habitof the whole group was to build open cup-shaped nests in more or lessexposed situations, the production of colour and marking in the female, by whatever cause, was continually checked by its rendering her tooconspicuous, while in the male it had free play, and developed in himthe most gorgeous hues. This, however, was not perhaps universally thecase; for where there was more than usual intelligence and capacity forchange of habits, the danger the female was exposed to by a partialbrightness of colour or marking might lead to the construction of aconcealed or covered nest, as in the case of the Tits and Hangnests. When this occurred, a special protection to the female would be nolonger necessary; so that the acquisition of colour and the modificationof the nest, might in some cases act and react on each other and attaintheir full development together. _Exceptional Cases confirmatory of the above Explanation. _ There exist a few very curious and anomalous facts in the naturalhistory of birds, which fortunately serve as crucial tests of the truthof this mode of explaining the inequalities of sexual colouration. Ithas been long known, that in some species the males either assisted in, or wholly performed, the act of incubation. It has also been oftennoticed, that in certain birds the usual sexual differences werereversed, the male being the more plainly coloured, the female more gayand often larger. I am not, however, aware that these two anomalies hadever been supposed to stand to each other in the relation of cause andeffect, till I adduced them in support of my views of the general theoryof protective adaptation. Yet it is undoubtedly the fact, that in thebest known cases in which the female bird is more conspicuously colouredthan the male, it is either positively ascertained that the latterperforms the duties of incubation, or there are good reasons forbelieving such to be the case. The most satisfactory example is that ofthe Gray Phalarope (Phalaropus fulicarius), the sexes of which are alikein winter, while in summer the female instead of the male takes on a gayand conspicuous nuptial plumage; but the male performs the duties ofincubation, sitting upon the eggs, which are laid upon the bare ground. In the Dotterell (Eudromias morinellus) the female is larger and morebrightly coloured than the male; and here, also, it is almost certainthat the latter sits upon the eggs. The Turnices of India also, have thefemale larger and often more brightly coloured; and Mr. Jerdon states, in his "Birds of India, " that the natives report, that, during thebreeding season, the females desert their eggs and associate in flocks, while the males are employed in hatching the eggs. In the few othercases in which the females are more brightly coloured, the habits arenot accurately known. The case of the Ostriches and Emeus will occur tomany as a difficulty, for here the male incubates, but is not lessconspicuous than the female; but there are two reasons why the case doesnot apply;--the birds are too large to derive any safety fromconcealment, from enemies which would devour the eggs they can defendthemselves by force, while to escape from their personal foes they trustto speed. We find, therefore, that a very large mass of facts relating to thesexual colouration and the mode of nidification of birds, including someof the most extraordinary anomalies to be found in their naturalhistory, can be shown to have an interdependent relation to each other, on the simple principle of the need of greater protection to that parentwhich performs the duties of incubation. Considering the very imperfectknowledge we possess of the habits of most extra-European birds, theexceptions to the prevalent rule are few, and generally occur inisolated species or in small groups; while several apparent exceptionscan be shown to be really confirmations of the law. _Real or apparent Exceptions to the Law stated at page 240. _ The only marked exceptions I have been able to discover are thefollowing:-- 1. King crows (Dicrourus). These birds are of a glossy black colour withlong forked tails. The sexes present no difference, and they build opennests. This apparent exception may probably be accounted for by the factthat these birds do not need the protection of a less conspicuouscolour. They are very pugnacious, and often attack and drive away crows, hawks, and kites; and as they are semi-gregarious in their habits, thefemales are not likely to be attacked while incubating. 2. Orioles (Oriolidæ). The true orioles are very gay birds; the sexesare, in many Eastern species, either nearly or quite alike, and thenests are open. This is one of the most serious exceptions, but it isone that to some extent proves the rule; for in this case it has beennoticed, that the parent birds display excessive care and solicitude inconcealing the nest among thick foliage, and in protecting theiroffspring by incessant and anxious watching. This indicates that thewant of protection consequent on the bright colour of the female makesitself felt, and is obviated by an increased development of the mentalfaculties. 3. Ground thrushes (Pittidæ). These elegant and brilliantly-colouredbirds are generally alike in both sexes, and build an open nest. It iscurious, however, that this is only an apparent exception, for almostall the bright colours are on the under surface, the back being usuallyolive green or brown, and the head black, with brown or whitish stripes, all which colours would harmonize with the foliage, sticks, and rootswhich surround the nest, built on or near the ground, and thus serve asa protection to the female bird. 4. Grallina Australis. This Australian bird is of strongly contrastedblack and white colours. The sexes are exactly alike, and it builds anopen clay nest in an exposed situation on a tree. This appears to be amost striking exception, but I am by no means sure that it is so. Werequire to know what tree it usually builds on, the colour of the barkor of the lichens that grow upon it, the tints of the ground, or ofother surrounding objects, before we can say that the bird, when sittingon its nest, is really conspicuous. It has been remarked that smallpatches of white and black blend at a short distance to form grey, oneof the commonest tints of natural objects. 5. Sunbirds (Nectarineidæ). In these beautiful little birds the malesonly are adorned with brilliant colours, the females being quite plain, yet they build covered nests in all the cases in which the nidificationis known. This is a negative rather than a positive exception to therule, since there may be other causes besides the need for protection, which prevent the female acquiring the gay colours of her mate, andthere is one curious circumstance which tends to elucidate it. The maleof Leptocoma zeylanica is said to assist in incubation. It is possible, therefore, that the group may originally have used open nests, and somechange of conditions, leading the male bird to sit, may have beenfollowed by the adoption of a domed nest. This is, however, the mostserious exception I have yet found to the general rule. 6. Superb warblers (Maluridæ). The males of these little birds areadorned with the most gorgeous colours, while the females are veryplain, yet they make domed nests. It is to be observed, however, thatthe male plumage is nuptial merely, and is retained for a very shorttime; the rest of the year both sexes are plain alike. It is probable, therefore, that the domed nest is for the protection of these delicatelittle birds against the rain, and that there is some unknown causewhich has led to the development of colour in the males only. There is one other case which at first sight looks like an exception, but which is far from being one in reality, and deserves to bementioned. In the beautiful Waxwing, (Bombycilla garrula, ) the sexes arevery nearly alike, and the elegant red wax tips to the wing-feathers arenearly, and sometimes quite, as conspicuous in the female as in themale. Yet it builds an open nest, and a person looking at the bird wouldsay it ought according to my theory to cover its nest. But it is, inreality, as completely protected by its colouration as the most plainlycoloured bird that flies. It breeds only in very high latitudes, and thenest, placed in fir-trees, is formed chiefly of lichens. Now thedelicate gray and ashy and purplish hues of the head and back, togetherwith the yellow of the wings and tail, are tints that exactly harmonizewith the colours of various species of lichens, while the brilliant redwax tips exactly represent the crimson fructification of the commonlichen, Cladonia coccifera. When sitting on its nest, therefore, thefemale bird will exhibit no colours that are not common to the materialsof which it is constructed; and the several tints are distributed inabout the same proportions as they occur in nature. At a short distancethe bird would be indistinguishable from the nest it is sitting on, orfrom a natural clump of lichens, and will thus be completely protected. I think I have now noticed all exceptions of any importance to the lawof dependence of sexual colour on nidification. It will be seen thatthey are very few in number, compared with those which support thegeneralization; and in several cases there are circumstances in thehabits or structure of the species that sufficiently explain them. It isremarkable also that I have found scarcely any _positive_ exceptions, that is, cases of very brilliant or conspicuous female birds in whichthe nest was not concealed. Much less can there be shown any group ofbirds, in which the females are all of decidedly conspicuous colours onthe upper surface, and yet sit in open nests. The many cases in whichbirds of dull colours in both sexes make domed or concealed nests, donot, of course, affect this theory one way or the other; since itspurpose is only to account for the fact, that brilliant females ofbrilliant males are _always_ found to have covered or hidden nests, while obscure females of brilliant males _almost always_ have open andexposed nests. The fact that all classes of nests occur with dullcoloured birds in both sexes merely shows, as I have stronglymaintained, that in most cases the character of the nest determines thecolouration of the female, and not _vice versâ_. If the views here advocated are correct, as to the various influencesthat have determined the specialities of every bird's nest, and thegeneral colouration of female birds, with their action and reaction oneach other, we can hardly expect to find evidence more complete thanthat here set forth. Nature is such a tangled web of complex relations, that a series of correspondences running through hundreds of species, genera, and families, in every part of the system, can hardly fail toindicate a true casual connexion; and when, of the two factors in theproblem, one can be shown to be dependent on the most deeply seated andthe most stable facts of structure and conditions of life, while theother is a character universally admitted to be superficial and easilymodified, there can be little doubt as to which is cause and whicheffect. _Various modes of Protection of Animals. _ But the explanation of the phenomenon here attempted does not rest aloneon the facts I have been able now to adduce. In the essay on "Mimicry, "it is shown how important a part the necessity for protection hasplayed, in determining the external form and colouration, and sometimeseven the internal structure of animals. As illustrating this latter point, I may refer to the remarkable hooked, branched, or star-like spiculæ in many sponges, which are believed tohave the function chiefly, of rendering them unpalatable to othercreatures. The Holothuridæ or sea-cucumbers possess a similarprotection, many of them having anchor-shaped spicules embedded in theirskin, as the Synapta; while others (Cuviera squamata) are covered with ahard calcareous pavement. Many of these are of a bright red or purplecolour, and are very conspicuous, while the allied Trepang, orBeche-de-mer (Holothuria edulis), which is not armed with any suchdefensive weapons, is of a dull sand-or mud-colour, so as hardly to bedistinguished from the sea bed on which it reposes. Many of the smallermarine animals are protected by their almost invisible transparency, while those that are most brightly coloured will be often found to havea special protection, either in stinging tentacles like Physalia, or ina hard calcareous crust, as in the star fishes. _Females of some Groups require and obtain more Protection than theMales. _ In the struggle for existence incessantly going on, protection orconcealment is one of the most general and most effectual means ofmaintaining life; and it is by modifications of colour that thisprotection can be most readily obtained, since no other character issubject to such numerous and rapid variations. The case I have nowendeavoured to illustrate is exactly analogous to what occurs amongbutterflies. As a general rule, the female butterfly is of dull andinconspicuous colours, even when the male is most gorgeously arrayed;but when the species is protected from attack by a disagreeable odour, as in the Heliconidæ, Danaidæ and Acroeidæ, both sexes display the sameor equally brilliant hues. Among the species which gain a protection byimitating these, the very weak and slow-flying Leptalides resemble themin both sexes, because both sexes alike require protection, while in themore active and strong-winged genera--Papilio, Pieris, and Diadema--itis generally the females only that mimic the protected groups, and indoing so often become actually more gay and more conspicuous than themales, thus reversing the usual and in fact almost universal charactersof the sexes. So, in the wonderful Eastern leaf-insects of the genusPhyllium, it is the female only that so marvellously imitates a greenleaf; and in all these cases the difference can be traced to the greaterneed of protection for the female, on whose continued existence, whiledepositing her eggs, the safety of the race depends. In Mammalia and inreptiles, however brilliant the colours may be, there is rarely anydifference between that of the sexes, because the female is notnecessarily more exposed to attack than the male. It may, I think, belooked upon as a confirmation of this view, that no single case is knowneither in the above-named genera--Papilio, Pieris, and Diadema--or inany other butterfly, of a male _alone_, mimicking one of the Danaidæ orHeliconidæ. Yet the necessary colour is far more abundant in the males, and variations always seem ready for any useful purpose. This seems todepend on the general law, that each species and each sex can only bemodified just as far as is absolutely necessary for it to maintainitself in the struggle for existence, not a step further. A male insectby its structure and habits is less exposed to danger, and also requiresless protection than the female. It cannot, therefore, alone acquire anyfurther protection through the agency of natural selection. But thefemale requires some extra protection, to balance the greater danger towhich she is exposed, and her greater importance to the existence of thespecies; and this she always acquires, in one way or another, throughthe action of natural selection. In his "Origin of Species, " fourth edition, p. 241, Mr. Darwinrecognises the necessity for protection as sometimes being a cause ofthe obscure colours of female birds; but he does not seem to consider itso very important an agent in modifying colour as I am disposed to do. In the same paragraph (p. 240), he alludes to the fact of female birdsand butterflies being sometimes very plain, sometimes as gay as themales; but, apparently, considers this mainly due to peculiar laws ofinheritance, which sometimes continue acquired colour in the line of onesex only, sometimes in both. Without denying the action of such a law(which Mr. Darwin informs me he has facts to support), I impute thedifference, in the great majority of cases, to the greater or less needof protection in the female sex in these groups of animals. This need was seen to exist a century ago by the Hon. Daines Barrington, who, in the article already quoted (see p. 220), after alluding to thefact that singing birds are all small, and suggesting (but I thinkerroneously) that this may have arisen from the difficulty larger birdswould have in concealing themselves if they called the attention oftheir enemies by loud notes, goes on thus:--"I should rather conceive itis for the same reason no hen bird sings, because this talent would bestill more dangerous during incubation, which _may possibly also accountfor the inferiority in point of plumage_. " This is a curiousanticipation of the main idea on which this essay is founded. It hasbeen unnoticed for near a century, and my attention was only recentlycalled to it by Mr. Darwin himself. _Conclusion. _ To some persons it will perhaps appear, that the causes to which Iimpute so much of the external aspect of nature are too simple, tooinsignificant, and too unimportant for such a mighty work. But I wouldask them to consider, that the great object of all the peculiarities ofanimal structure is to preserve the life of the individual, and tomaintain the existence of the species. Colour has hitherto been toooften looked upon as something adventitious and superficial, somethinggiven to an animal not to be useful to itself, but solely to gratify manor even superior beings--to add to the beauty and ideal harmony ofnature. If this were the case, then, it is evident that the colours oforganised beings would be an exception to most other natural phenomena. They would not be the product of general laws, or determined byever-changing external conditions; and we must give up all enquiry intotheir origin and causes, since (by the hypothesis) they are dependent ona Will whose motives must ever be unknown to us. But, strange to say, nosooner do we begin to examine and classify the colours of naturalobjects, than we find that they are intimately related to a variety ofother phenomena, and are, like them, strictly subordinated to generallaws. I have here attempted to elucidate some of these laws in the caseof birds, and have shown how the mode of nidification has affected thecolouring of the female sex in this group. I have before shown to howgreat an extent, and in how many ways, the need of protection hasdetermined the colours of insects, and of some groups of reptiles andmammalia, and I would now call particular attention to the fact that thegay tints of flowers, so long supposed to be a convincing proof thatcolour has been bestowed for other purposes than the good of itspossessor, have been shown by Mr. Darwin to follow the same great law ofutility. Flowers do not often need protection, but very often requirethe aid of insects to fertilize them, and maintain their reproductivepowers in the greatest vigour. Their gay colours attract insects, as doalso their sweet odours and honeyed secretions; and that this is themain function of colour in flowers is shown by the striking fact, thatthose flowers which can be perfectly fertilized by the wind, and do notneed the aid of insects, _rarely or never have gaily-coloured flowers_. This wide extension of the general principle of utility to the coloursof such varied groups, both in the animal and vegetable kingdoms, compels us to acknowledge that the "reign of law" has been fairly tracedinto this stronghold of the advocates of special creation. And to thosewho oppose the explanation I have given of the facts adduced in thisessay, I would again respectfully urge that they must grapple with thewhole of the facts, not one or two of them only. It will be admittedthat, on the theory of evolution and natural selection, a wide range offacts with regard to colour in nature have been co-ordinated andexplained. Until at least an equally wide range of facts can be shown tobe in harmony with any other theory, we can hardly be expected toabandon that which has already done such good service, and which has ledto the discovery of so many interesting and unexpected harmonies amongthe most common (but hitherto most neglected and least understood), ofthe phenomena presented by organised beings. VIII. CREATION BY LAW. Among the various criticisms that have appeared on Mr. Darwin'scelebrated "Origin of Species, " there is, perhaps, none that will appealto so large a number of well educated and intelligent persons, as thatcontained in the Duke of Argyll's "Reign of Law. " The noble authorrepresents the feelings and expresses the ideas of that large class, whotake a keen interest in the progress of Science in general, andespecially that of Natural History, but have never themselves studiednature in detail, or acquired that personal knowledge of the structureof closely allied forms, --the wonderful gradations from species tospecies and from group to group, and the infinite variety of thephenomena of "variation" in organic beings, --which are absolutelynecessary for a full appreciation of the facts and reasonings containedin Mr. Darwin's great work. Nearly half of the Duke's book is devoted to an exposition of his ideaof "Creation by Law, " and he expresses so clearly what are hisdifficulties and objections as regards the theory of "NaturalSelection, " that I think it advisable that they should be fairlyanswered, and that his own views should be shown to lead to conclusions, as hard to accept as any which he imputes to Mr. Darwin. The point on which the Duke of Argyll lays most stress, is, that proofsof Mind everywhere meet us in Nature, and are more especially manifestwherever we find "contrivance" or "beauty. " He maintains that thisindicates the constant supervision and direct interference of theCreator, and cannot possibly be explained by the unassisted action ofany combination of laws. Now, Mr. Darwin's work has for its main object, to show, that all the phenomena of living things, --all their wonderfulorgans and complicated structures, their infinite variety of form, size, and colour, their intricate and involved relations to each other, --mayhave been produced by the action of a few general laws of the simplestkind, laws which are in most cases mere statements of admitted facts. The chief of these laws or facts are the following:-- 1. _The Law of Multiplication in Geometrical Progression. _--Allorganized beings have enormous powers of multiplication. Even man, whoincreases slower than all other animals, could under the most favourablecircumstances double his numbers every fifteen years, or a hundred-foldin a century. Many animals and plants could increase their numbers fromten to a thousand-fold every year. 2. _The Law of Limited Populations. _--The number of living individualsof each species in any country, or in the whole globe, is practicallystationary; whence it follows that the whole of this enormous increasemust die off almost as fast as produced, except only those individualsfor whom room is made by the death of parents. As a simple but strikingexample, take an oak forest. Every oak will drop annually thousands ormillions of acorns, but till an old tree falls, not one of thesemillions can grow up into an oak. They must die at various stages ofgrowth. 3. _The Law of Heredity, or Likeness of Offspring to theirParents. _--This is a universal, but not an absolute law. All creaturesresemble their parents in a high degree, and in the majority of casesvery accurately; so that even individual peculiarities, of whateverkind, in the parents, are almost always transmitted to some of theoffspring. 4. _The Law of Variation. _--This is fully expressed by the lines:-- "No being on this earthly ball, Is like another, all in all. " Offspring resemble their parents very much, but not wholly--each beingpossesses its individuality. This "variation" itself varies in amount, but it is always present, not only in the whole being, but in every partof every being. Every organ, every character, every feeling isindividual; that is to say, _varies_ from the same organ, character, orfeeling in every other individual. 5. _The Law of unceasing Change of Physical Conditions upon the Surfaceof the Earth. _--Geology shows us that this change has always gone on intimes past, and we also know that it is now everywhere going on. 6. _The Equilibrium or Harmony of Nature. _--When a species is welladapted to the conditions which environ it, it flourishes; whenimperfectly adapted it decays; when ill-adapted it becomes extinct. If_all_ the conditions which determine an organism's well-being are takeninto consideration, this statement can hardly be disputed. * * * * * This series of facts or laws, are mere statements of what is thecondition of nature. They are facts or inferences which are generallyknown, generally admitted--but in discussing the subject of the "Originof Species"--as generally forgotten. It is from these universallyadmitted facts, that the origin of all the varied forms of nature may bededuced by a logical chain of reasoning, which, however, is at everystep verified and shown to be in strict accord with facts; and, at thesame time, many curious phenomena which can by no other means beunderstood, are explained and accounted for. It is probable, that theseprimary facts or laws are but results of the very nature of life, and ofthe essential properties of organized and unorganized matter. Mr. Herbert Spencer, in his "First Principles" and his "Biology" has, Ithink, made us able to understand how this may be; but at present we mayaccept these simple laws without going further back, and the questionthen is--whether the variety, the harmony, the contrivance, and thebeauty we perceive in organic beings, can have been produced by theaction of these laws alone, or whether we are required to believe in theincessant interference and direct action of the mind and will of theCreator. It is simply a question of how the Creator has worked. TheDuke (and I quote him as having well expressed the views of the moreintelligent of Mr. Darwin's opponents) maintains, that He has personallyapplied general laws to produce effects, which those laws are not inthemselves capable of producing; that the universe alone, with all itslaws intact, would be a sort of chaos, without variety, without harmony, without design, without beauty; that there is not (and therefore we maypresume that there could not be) any self-developing power in theuniverse. I believe, on the contrary, that the universe is soconstituted as to be self-regulating; that as long as it contains Life, the forms under which that life is manifested have an inherent power ofadjustment to each other and to surrounding nature; and that thisadjustment necessarily leads to the greatest amount of variety andbeauty and enjoyment, because it does depend on general laws, and not ona continual supervision and re-arrangement of details. As a matter offeeling and religion, I hold this to be a far higher conception of theCreator and of the Universe than that which may be called the "continualinterference" hypothesis; but it is not a question to be decided by ourfeelings or convictions, it is a question of facts and of reason. Couldthe change, which Geology shows us has ever taken place in the forms oflife, have been produced by general laws, or does it imperativelyrequire the incessant supervision of a creative mind? This is thequestion for us to consider, and our opponents have the difficult taskof proving a negative, if we show that there are both facts andanalogies in our favour. _Mr. Darwin's Metaphors liable to Misconception. _ Mr. Darwin has laid himself open to much misconception, and has given tohis opponents a powerful weapon against himself, by his continual use ofmetaphor in describing the wonderful co-adaptations of organic beings. "It is curious, " says the Duke of Argyll, "to observe the languagewhich this most advanced disciple of pure naturalism instinctivelyuses, when he has to describe the complicated structure of this curiousorder of plants (the Orchids). 'Caution in ascribing intentions tonature, ' does not seem to occur to him as possible. Intention is the onething which he does see, and which, when he does not see, he seeks fordiligently until he finds it. He exhausts every form of words and ofillustration, by which intention or mental purpose can be described. 'Contrivance'--'curious contrivance, '--'beautiful contrivance, '--theseare expressions which occur over and over again. Here is one sentencedescribing the parts of a particular species: 'the Labellum is developedinto a long nectary, _in order_ to attract Lepidoptera, and we shallpresently give reason for suspecting that the nectar is _purposely_ solodged, that it can be sucked only slowly _in order_ to give time forthe curious chemical quality of the viscid matter setting hard anddry. '" Many other examples of similar expressions are quoted by theDuke, who maintains that no explanation of these "contrivances" hasbeen or can be given, except on the supposition of a personal contriver, specially arranging the details of each case, although causing them tobe produced by the ordinary processes of growth and reproduction. Now there is a difficulty in this view of the origin of the structure ofOrchids which the Duke does not allude to. The majority of floweringplants are fertilized, either without the agency of insects or, wheninsects are required, without any very important modification of thestructure of the flower. It is evident, therefore, that flowers mighthave been formed as varied, fantastic, and beautiful as the Orchids, andyet have been fertilized without more complexity of structure than isfound in Violets, or Clover, or Primroses, or a thousand other flowers. The strange springs and traps and pitfalls found in the flowers ofOrchids cannot be necessary _per se_, since exactly the same end isgained in ten thousand other flowers which do not possess them. Is itnot then an extraordinary idea, to imagine the Creator of the Universe_contriving_ the various complicated parts of these flowers, as amechanic might contrive an ingenious toy or a difficult puzzle? Is itnot a more worthy conception that they are some of the results of thosegeneral laws which were so co-ordinated at the first introduction oflife upon the earth as to result necessarily in the utmost possibledevelopment of varied forms? But let us take one of the simpler cases adduced and see if our generallaws are unable to account for it. _A Case of Orchis-structure explained by Natural Selection. _ There is a Madagascar Orchis--the Angræcum sesquipedale--with animmensely long and deep nectary. How did such an extraordinary organcome to be developed? Mr. Darwin's explanation is this. The pollen ofthis flower can only be removed by the base of the proboscis of somevery large moths, when trying to get at the nectar at the bottom of thevessel. The moths with the longest probosces would do this mosteffectually; they would be rewarded for their long tongues by gettingthe most nectar; whilst on the other hand, the flowers with the deepestnectaries would be the best fertilized by the largest moths preferringthem. Consequently, the deepest nectaried Orchids and the longesttongued moths would each confer on the other an advantage in the battleof life. This would tend to their respective perpetuation, and to theconstant lengthening of nectaries and probosces. Now let it beremembered, that what we have to account for, is only the unusual lengthof this organ. A nectary is found in many orders of plants and isespecially common in the Orchids, but in this one case only is it morethan a foot long. How did this arise? We begin with the fact, provedexperimentally by Mr. Darwin, that moths do visit Orchids, do thrusttheir spiral trunks into the nectaries, and do fertilize them bycarrying the pollinia of one flower to the stigma of another. He hasfurther explained the exact mechanism by which this is effected, andthe Duke of Argyll admits the accuracy of his observations. In ourBritish species, such as Orchis pyramidalis, it is not necessary thatthere should be any exact adjustment between the length of the nectaryand that of the proboscis of the insect; and thus a number of insects ofvarious sizes are found to carry away the pollinia and aid in thefertilization. In the Angræcum sesquipedale, however, it is necessarythat the proboscis should be forced into a particular part of theflower, and this would only be done by a large moth burying itsproboscis to the very base, and straining to drain the nectar from thebottom of the long tube, in which it occupies a depth of one or twoinches only. Now let us start from the time when the nectary was onlyhalf its present length or about six inches, and was chiefly fertilizedby a species of moth which appeared at the time of the plant'sflowering, and whose proboscis was of the same length. Among themillions of flowers of the Angræcum produced every year, some wouldalways be shorter than the average, some longer. The former, owing tothe structure of the flower, would not get fertilized, because the mothscould get all the nectar without forcing their trunks down to the verybase. The latter would be well fertilized, and the longest would on theaverage be the best fertilized of all. By this process alone the averagelength of the nectary would annually increase, because, theshort-nectaried flowers being sterile and the long ones having abundantoffspring, exactly the same effect would be produced as if a gardenerdestroyed the short ones and sowed the seed of the long ones only; andthis we know by experience would produce a regular increase of length, since it is this very process which has increased the size and changedthe form of our cultivated fruits and flowers. But this would lead in time to such an increased length of the nectarythat many of the moths could only just reach the surface of the nectar, and only the few with exceptionally long trunks be able to suck up aconsiderable portion. This would cause many moths to neglect these flowers because they couldnot get a satisfying supply of nectar, and if these were the only mothsin the country the flowers would undoubtedly suffer, and the furthergrowth of the nectary be checked by exactly the same process which hadled to its increase. But there are an immense variety of moths, ofvarious lengths of proboscis, and as the nectary became longer, otherand larger species would become the fertilizers, and would carry on theprocess till the largest moths became the sole agents. Now, if notbefore, the moth would also be affected, for those with the longestprobosces would get most food, would be the strongest and most vigorous, would visit and fertilize the greatest number of flowers, and wouldleave the largest number of descendants. The flowers most completelyfertilized by these moths being those which had the longest nectaries, there would in each generation be on the average an increase in thelength of the nectaries, and also an average increase in the length ofthe probosces of the moths; and this would be a _necessary result_ fromthe fact that nature ever fluctuates about a mean, or that in everygeneration there would be flowers with longer and shorter nectaries, andmoths with longer and shorter probosces than the average. No doubt thereare a hundred causes that might have checked this process before it hadreached the point of development at which we find it. If, for instance, the variation in the quantity of nectar had been at any stage greaterthan the variation in the length of the nectary, then smaller mothscould have reached it and have effected the fertilization. Or if thegrowth of the probosces of the moths had from other causes increasedquicker than that of the nectary, or if the increased length ofproboscis had been injurious to them in any way, or if the species ofmoth with the longest proboscis had become much diminished by some enemyor other unfavourable conditions, then, in any of these cases, theshorter nectaried flowers, which would have attracted and could havebeen fertilized by the smaller kinds of moths, would have had theadvantage. And checks of a similar nature to these no doubt have actedin other parts of the world, and have prevented such an extraordinarydevelopment of nectary as has been produced by favourable conditions inMadagascar only, and in one single species of Orchid. I may here mentionthat some of the large Sphinx moths of the tropics have probosces nearlyas long as the nectary of Angræcum sesquipedale. I have carefullymeasured the proboscis of a specimen of Macrosila cluentius from SouthAmerica, in the collection of the British Museum, and find it to be nineinches and a quarter long! One from tropical Africa (Macrosila morganii)is seven inches and a half. A species having a proboscis two or threeinches longer could reach the nectar in the largest flowers of Angræcumsesquipedale, whose nectaries vary in length from ten to fourteeninches. That such a moth exists in Madagascar may be safely predicted;and naturalists who visit that island should search for it with as muchconfidence as Astronomers searched for the planet Neptune, --and Iventure to predict they will be equally successful! Now, instead of this beautiful self-acting adjustment, the opposingtheory is, that the Creator of the Universe, by a direct act of hisWill, so disposed the natural forces influencing the growth of this onespecies of plant as to cause its nectary to increase to this enormouslength; and at the same time, by an equally special act, determined theflow of nourishment in the organization of the moth, so as to cause itsproboscis to increase in exactly the same proportion, having previouslyso constructed the Angræcum that it could only be maintained inexistence by the agency of this moth. But what proof is given orsuggested that this was the mode by which the adjustment took place?None whatever, except a feeling that there is an adjustment of adelicate kind, and an inability to see how known causes could haveproduced such an adjustment. I believe I have shown, however, that suchan adjustment is not only possible but inevitable, unless at some pointor other we deny the action of those simple laws which we have alreadyadmitted to be but the expressions of existing facts. _Adaptation brought about by General Laws. _ It is difficult to find anything like parallel cases in inorganicnature, but that of a river may perhaps illustrate the subject in somedegree. Let us suppose a person totally ignorant of Modern Geology tostudy carefully a great River System. He finds in its lower part, a deepbroad channel filled to the brim, flowing slowly through a flat countryand carrying out to the sea a quantity of fine sediment. Higher up itbranches into a number of smaller channels, flowing alternately throughflat valleys and between high banks; sometimes he finds a deep rocky bedwith perpendicular walls, carrying the water through a chain of hills;where the stream is narrow he finds it deep, where wide shallow. Furtherup still, he comes to a mountainous region, with hundreds of streams andrivulets, each with its tributary rills and gullies, collecting thewater from every square mile of surface, and every channel adapted tothe water that it has to carry. He finds that the bed of every branch, and stream, and rivulet, has a steeper and steeper slope as itapproaches its sources, and is thus enabled to carry off the water fromheavy rains, and to bear away the stones and pebbles and gravel, thatwould otherwise block up its course. In every part of this system hewould see exact adaptation of means to an end. He would say, that thissystem of channels must have been designed, it answers its purpose soeffectually. Nothing but a mind could have so exactly adapted the slopesof the channels, their capacity, and frequency, to the nature of thesoil and the quantity of the rainfall. Again, he would see specialadaptation to the wants of man, in broad quiet navigable rivers flowingthrough fertile plains that support a large population, while the rockystreams and mountain torrents, were confined to those sterile regionssuitable only for a small population of shepherds and herdsmen. He wouldlisten with incredulity to the Geologist, who assured him, that theadaptation and adjustment he so admired was an inevitable result of theaction of general laws. That the rains and rivers, aided by subterraneanforces, had modelled the country, had formed the hills and valleys, hadscooped out the river beds, and levelled the plains;--and it would onlybe after much patient observation and study, after having watched theminute changes produced year by year, and multiplying them by thousandsand ten thousands, after visiting the various regions of the earth andseeing the changes everywhere going on, and the unmistakable signs ofgreater changes in past times, --that he could be made to understand thatthe surface of the earth, however beautiful and harmonious it mayappear, is strictly due in every detail to the action of forces whichare demonstrably self-adjusting. Moreover, when he had sufficiently extended his inquiries, he wouldfind, that every evil effect which he would imagine must be the resultof non-adjustment does somewhere or other occur, only it is not alwaysevil. Looking on a fertile valley, he would perhaps say--"If the channelof this river were not well adjusted, if for a few miles it sloped thewrong way, the water could not escape, and all this luxuriant valley, full of human beings, would become a waste of waters. " Well, there arehundreds of such cases. Every lake is a valley "wasted by water, " and insome cases (as the Dead Sea) it is a positive evil, a blot upon theharmony and adaptation of the surface of the earth. Again, he mightsay--"If rain did not fall here, but the clouds passed over us to someother regions, this verdant and highly cultivated plain would become adesert. " And there are such deserts over a large part of the earth, which abundant rains would convert into pleasant dwelling-places forman. Or he might observe some great navigable river, and reflect howeasily rocks, or a steeper channel in places, might render it useless toman;--and a little inquiry would show him hundreds of rivers in everypart of the world, which are thus rendered useless for navigation. Exactly the same thing occurs in organic nature. We see some onewonderful case of adjustment, some unusual development of an organ, butwe pass over the hundreds of cases in which that adjustment anddevelopment do not occur. No doubt when one adjustment is absent anothertakes its place, because no organism can continue to exist that is notadjusted to its environment; and unceasing variation with unlimitedpowers of multiplication, in most cases, furnish the means ofself-adjustment. The world is so constituted, that by the action ofgeneral laws there is produced the greatest possible variety of surfaceand of climate; and by the action of laws equally general, the greatestpossible variety of organisms have been produced, adapted to the variedconditions of every part of the earth. Tho objector would probablyhimself admit, that the varied surface of the earth--the plains andvalleys, the hills and mountains, the deserts and volcanoes, the windsand currents, the seas and lakes and rivers, and the various climates ofthe earth--are all the results of general laws acting and re-actingduring countless ages; and that the Creator does not appear to guide andcontrol the action of these laws--here determining the height of amountain, there altering the channel of a river--here making the rainsmore abundant, there changing the direction of a current. He wouldprobably admit that the forces of inorganic nature are self-adjusting, and that the result necessarily fluctuates about a given mean condition(which is itself slowly changing), while within certain limits thegreatest possible amount of variety is produced. If then a "contrivingmind" is not necessary at every step of the process of change eternallygoing on in the inorganic world, why are we required to believe in thecontinual action of such a mind in the region of organic nature? True, the laws at work are more complex, the adjustments more delicate, theappearance of special adaptation more remarkable; but why should wemeasure the creative mind by our own? Why should we suppose the machinetoo complicated, to have been designed by the Creator so complete thatit would necessarily work out harmonious results? The theory of"continual interference" is a limitation of the Creator's power. Itassumes that he could not work by pure law in the organic, as he hasdone in the inorganic world; it assumes that he could not foresee theconsequences of the laws of matter and mind combined--that results wouldcontinually arise which are contrary to what is best, and that he has tochange what would otherwise be the course of nature, in order to producethat beauty, and variety, and harmony, which even we, with our limitedintellects, can conceive to be the result of self-adjustment in auniverse governed by unvarying law. If we could not conceive the worldof nature to be self-adjusting and capable of endless development, itwould even then be an unworthy idea of a Creator, to impute theincapacity of our minds to him; but when many human minds can conceive, and can even trace out in detail some of the adaptations in nature asthe necessary results of unvarying law, it seems strange that, in theinterests of religion, any one should seek to prove that the System ofNature, instead of being above, is far below our highest conceptions ofit. I, for one, cannot believe that the world would come to chaos ifleft to Law alone. I cannot believe that there is in it no inherentpower of developing beauty or variety, and that the direct action of theDeity is required to produce each spot or streak on every insect, eachdetail of structure in every one of the millions of organisms that liveor have lived upon the earth. For it is impossible to draw a line. Ifany modifications of structure could be the result of law, why not all?If some self-adaptations could arise, why not others? If any varietiesof colour, why not all the varieties we see? No attempt is made toexplain this, except by reference to the fact that "purpose" and"contrivance" are everywhere visible, and by the illogical deductionthat they could only have arisen from the direct action of some mind, because the direct action of our minds produces similar "contrivances";but it is forgotten that adaptation, however produced, must have theappearance of design. The channel of a river looks as if made _for_ theriver, although it is made _by_ it; the fine layers and beds in adeposit of sand, often look as if they had been sorted, and sifted, andlevelled, designedly; the sides and angles of a crystal exactly resemblesimilar forms designed by man; but we do not therefore conclude thatthese effects have, in each individual case, required the directingaction of a creative mind, or see any difficulty in their being producedby natural Law. _Beauty in Nature. _ Let us, however, leave this general argument for a while, and turn toanother special case, which has been appealed to as conclusive againstMr. Darwin's views. "Beauty" is, to some persons, as great astumbling-block as "contrivance. " They cannot conceive a system of theUniverse, so perfect, as necessarily to develop every form of Beauty, but suppose that when anything specially beautiful occurs, it is a stepbeyond what that system could have produced, something which the Creatorhas added for his own delectation. Speaking of the Humming Birds, the Duke of Argyll says: "In the firstplace, it is to be observed of the whole group, that there is noconnection which can be traced or conceived, between the splendour ofthe humming birds and any function essential to their life. If therewere any such connection, that splendour could not be confined, as italmost exclusively is, to only one sex. The female birds are, of course, not placed at any disadvantage in the struggle for existence by theirmore sombre colouring. " And after describing the various ornaments ofthese birds, he says: "Mere ornament and variety of form, and these fortheir own sake, is the only principle or rule with reference to whichCreative Power seems to have worked in these wonderful and beautifulbirds.... A crest of topaz is no better in the struggle for existencethan a crest of sapphire. A frill ending in spangles of the emerald isno better in the battle of life than a frill ending in spangles of theruby. A tail is not affected for the purposes of flight, whether itsmarginal or its central feathers are decorated with white.... Merebeauty and mere variety, for their own sake, are objects which weourselves seek when we can make the Forces of Nature subordinate to theattainment of them. There seems to be no conceivable reason why weshould doubt or question, that these are ends and aims also in the formsgiven to living organisms" ("Reign of Law, " p. 248). Here the statement that "no connection can be conceived between thesplendour of the humming birds and any function essential to theirlife, " is met by the fact, that Mr. Darwin has not only conceived buthas shown, both by observation and reasoning, how beauty of colour andform may have a direct influence on the most important of all thefunctions of life, that of reproduction. In the variations to whichbirds are subject, any more brilliant colour than usual would beattractive to the females, and would lead to the individuals so adornedleaving more than the average number of offspring. Experiment andobservation have shown, that this kind of sexual selection does actuallytake place; and the laws of inheritance would necessarily lead to thefurther development of any individual peculiarity that was attractive, and thus the splendour of the humming birds is directly connected withtheir very existence. It is true that "a crest of topaz may be no betterthan a crest of sapphire, " but either of these may be much better thanno crest at all; and the different conditions under which the parentform must have existed in different parts of its range, will havedetermined different variations of tint, either of which wereadvantageous. The reason why female birds are not adorned with equallybrilliant plumes is sufficiently clear; they would be injurious, byrendering their possessors too conspicuous during incubation. Survivalof the fittest, has therefore favoured the development of those darkgreen tints on the upper surface of so many female humming birds, whichare most conducive to their protection while the important functions ofhatching and rearing the young are being carried on. Keeping in mind thelaws of multiplication, variation, and survival of the fittest, whichare for ever in action, these varied developments of beauty andharmonious adjustments to conditions, are not only conceivable butdemonstrable results. The objection I am now combating is solely founded on the supposedanalogy of the Creator's mind to ours, as regards the love of Beauty forits own sake; but if this analogy is to be trusted, then there ought tobe no natural objects which are disagreeable or ungraceful in our eyes. And yet it is undoubtedly the fact that there are many such. Just assurely as the Horse and Deer are beautiful and graceful, the Elephant, Rhinoceros, Hippopotamus, and Camel are the reverse. The majority ofMonkeys and Apes are not beautiful; the majority of Birds have no beautyof colour; a vast number of Insects and Reptiles are positively ugly. Now, if the Creator's mind is like ours, whence this ugliness? It isuseless to say "that is a mystery we cannot explain, " because we haveattempted to explain one-half of creation by a method that will notapply to the other half. We know that a man with the highest taste andwith unlimited wealth, practically does abolish all ungraceful anddisagreeable forms and colours from his own domains. If the beauty ofcreation is to be explained by the Creator's love of beauty, we arebound to ask why he has not banished deformity from the earth, as thewealthy and enlightened man does from his estate and from his dwelling;and if we can get no satisfactory answer, we shall do well to reject theexplanation offered. Again, in the case of flowers, which are alwaysespecially referred to, as the surest evidence of beauty being an end ofitself in creation, the whole of the facts are never fairly met. Atleast half the plants in the world have not bright-coloured or beautifulflowers; and Mr. Darwin has lately arrived at the wonderfulgeneralization, that flowers have become beautiful solely to attractinsects to assist in their fertilization. He adds, "I have come to thisconclusion from finding it an invariable rule, that when a flower isfertilized by the wind it never has a gaily-coloured corolla. " Here is amost wonderful case of beauty being _useful_, when it might be leastexpected. But much more is proved; for when beauty is of no use to theplant it is not given. It cannot be imagined to do any harm. It issimply not necessary, and is therefore withheld! We ought surely to havebeen told how this fact is consistent with beauty being "an end initself, " and with the statement of its being given to natural objects"for its own sake. " _How new Forms are produced by Variation and Selection. _ Let us now consider another of the popular objections which the Duke ofArgyll thus sets forth:-- "Mr. Darwin does not pretend to have discovered any law or rule, according to which new Forms have been born from old Forms. He does nothold that outward conditions, however changed, are sufficient to accountfor them.... His theory seems to be far better than a mere theory--to bean established scientific truth--in so far as it accounts, in part atleast, for the success and establishment and spread of new Forms _whenthey have arisen_. But it does not even suggest the law under which, orby or according to which, such new Forms are introduced. NaturalSelection can do nothing, except with the materials presented to itshands. It cannot select except among the things open to selection.... Strictly speaking, therefore, Mr. Darwin's theory is not a theory on theOrigin of Species at all, but only a theory on the causes which lead tothe relative success or failure of such new forms as may be born intothe world. " ("Reign of Law, " p. 230. ) In this, and many other passages in his work, the Duke of Argyll setsforth his idea of Creation as a "Creation by birth, " but maintains thateach birth of a new form from parents differing from itself, has beenproduced by a special interference of the Creator, in order to directthe process of development into certain channels; that each new speciesis in fact a "special creation, " although brought into existence throughthe ordinary laws of reproduction. He maintains therefore, that the lawsof multiplication and variation cannot furnish the right kinds ofmaterials at the right times for natural selection to work on. Ibelieve, on the contrary, that it can be logically _proved_ from the sixaxiomatic laws before laid down, that such materials would be furnished;but I prefer to show there are abundance of _facts_ which demonstratethat they are furnished. The experience of all cultivators of plants and breeders of animalsshows, that when a sufficient number of individuals are examined, variations of any required kind can always be met with. On this dependsthe possibility of obtaining breeds, races, and fixed varieties ofanimals and plants; and it is found, that any one form of variation maybe accumulated by selection, without materially affecting the othercharacters of the species; each _seems_ to vary in the one requireddirection only. For example, in turnips, radishes, potatoes, andcarrots, the root or tuber varies in size, colour, form, and flavour, while the foliage and flowers seem to remain almost stationary; in thecabbage and lettuce, on the contrary, the foliage can be modified intovarious forms and modes of growth, the root, flower, and fruit remaininglittle altered; in the cauliflower and brocoli the flower heads vary; inthe garden pea the pod only changes. We get innumerable forms of fruitin the apple and pear, while the leaves and flowers remainundistinguishable; the same occurs in the gooseberry and garden currant. Directly however, (in the very same genus) we want the flower to vary inthe Ribes sanguineum, it does so, although mere cultivation for hundredsof years has not produced marked differences in the flowers of Ribesgrossularia. When fashion demands any particular change in the form orsize, or colour of a flower, sufficient variation always occurs in theright direction, as is shown by our roses, auriculas, and geraniums;when, as recently, ornamental leaves come into fashion sufficientvariation is found to meet the demand, and we have zoned pelargoniums, and variegated ivy, and it is discovered that a host of our commonestshrubs and herbaceous plants have taken to vary in this direction justwhen we want them to do so! This rapid variation is not confined to oldand well-known plants subjected for a long series of generations tocultivation, but the Sikim Rhododendrons, the Fuchsias, and Calceolariasfrom the Andes, and the Pelargoniums from the Cape are equallyaccommodating, and vary just when and where and how we require them. Turning to animals we find equally striking examples. If we want anyspecial quality in any animal we have only to breed it in sufficientquantities and watch carefully, and the required variety is _always_found, and can be increased to almost any desired extent. In Sheep, weget flesh, fat, and wool; in Cows, milk; in Horses, colour, strength, size, and speed; in Poultry, we have got almost any variety of colour, curious modifications of plumage, and the capacity of perpetualegg-laying. In Pigeons we have a still more remarkable proof of theuniversality of variation, for it has been at one time or another thefancy of breeders to change the form of every part of these birds, andthey have never found the required variations absent. The form, size, and shape of bill and feet, have been changed to such a degree as isfound only in distinct genera of wild birds; the number of tail feathershas been increased, a character which is generally one of the mostpermanent nature, and is of high importance in the classification ofbirds; and the size, the colour, and the habits, have been also changedto a marvellous extent. In Dogs, the degree of modification and thefacility with which it is effected, is almost equally apparent. Look atthe constant amount of variation in opposite directions that must havebeen going on, to develop the poodle and the greyhound from the sameoriginal stock! Instincts, habits, intelligence, size, speed, form, andcolour, have always varied, so as to produce the very races which thewants or fancies or passions of men may have led them to desire. Whetherthey wanted a bull-dog to torture another animal, a greyhound to catcha hare, or a bloodhound to hunt down their oppressed fellow-creatures, the required variations have always appeared. Now this great mass of facts, of which a mere sketch has been heregiven, are fully accounted for by the "Law of Variation" as laid down atthe commencement of this paper. Universal variability--small in amountbut in every direction, ever fluctuating about a mean condition untilmade to advance in a given direction by "election, " natural orartificial, --is the simple basis for the indefinite modification of theforms of life;--partial, unbalanced, and consequently unstablemodifications being produced by man, while those developed under theunrestrained action of natural laws, are at every step self-adjusted toexternal conditions by the dying out of all unadjusted forms, and aretherefore stable and comparatively permanent. To be consistent in theirviews, our opponents must maintain that every one of the variations thathave rendered possible the changes produced by man, have been determinedat the right time and place by the will of the Creator. Every raceproduced by the florist or the breeder, the dog or the pigeon fancier, the ratcatcher, the sporting man, or the slave-hunter, must have beenprovided for by varieties occurring when wanted; and as these variationswere never withheld, it would prove, that the sanction of an all-wiseand all-powerful Being, has been given to that which the highest humanminds consider to be trivial, mean, or debasing. This appears to be a complete answer to the theory, that variationsufficient in amount to be accumulated in a given direction must be thedirect act of the Creative Mind, but it is also sufficiently condemnedby being so entirely unnecessary. The facility with which man obtainsnew races, depends chiefly upon the number of individuals he can procureto select from. When hundreds of florists or breeders are all aiming atthe same object, the work of change goes on rapidly. But a commonspecies in nature contains a thousand-or a million-fold more individualsthan any domestic race; and survival of the fittest must unerringlypreserve all that vary in the right direction, not only in obviouscharacters but in minute details, not only in external but in internalorgans; so that if the materials are sufficient for the needs of man, there can be no want of them to fulfil the grand purpose of keeping up asupply of modified organisms, exactly adapted to the changed conditionsthat are always occurring in the inorganic world. _The Objection that there are Limits to Variation. _ Having now, I believe, fairly answered the chief objections of the Dukeof Argyll, I proceed to notice one or two of those adduced in an ableand argumentative essay on the "Origin of Species" in the _North BritishReview_ for July, 1867. The writer first attempts to prove that thereare strict limits to variation. When we begin to select variations inany one direction, the process is comparatively rapid, but after aconsiderable amount of change has been effected it becomes slower andslower, till at length its limits are reached and no care in breedingand selection can produce any further advance. The race-horse is chosenas an example. It is admitted that, with any ordinary lot of horses tobegin with, careful selection would in a few years make a greatimprovement, and in a comparatively short time the standard of our bestracers might be reached. But that standard has not for many years beenmaterially raised, although unlimited wealth and energy are expended inthe attempt. This is held to prove that there are definite limits tovariation in any special direction, and that we have no reason tosuppose that mere time, and the selective process being carried on bynatural law, could make any material difference. But the writer does notperceive that this argument fails to meet the real question, which is, not whether indefinite and unlimited change in any or all directions ispossible, but whether such differences as do occur in nature could havebeen produced by the accumulation of variations by selection. In thematter of speed, a limit of a definite kind as regards land animals doesexist in nature. All the swiftest animals--deer, antelopes, hares, foxes, lions, leopards, horses, zebras, and many others, have reachedvery nearly the same degree of speed. Although the swiftest of each musthave been for ages preserved, and the slowest must have perished, wehave no reason to believe there is any advance of speed. The possiblelimit under existing conditions, and perhaps under possible terrestrialconditions, has been long ago reached. In cases, however, where thislimit had not been so nearly reached as in the horse, we have beenenabled to make a more marked advance and to produce a greaterdifference of form. The wild dog is an animal that hunts much incompany, and trusts more to endurance than to speed. Man has producedthe greyhound, which differs much more from the wolf or the dingo thanthe racer does from the wild Arabian. Domestic dogs, again, have variedmore in size and in form than the whole family of Canidæ in a state ofnature. No wild dog, fox, or wolf, is either so small as some of thesmallest terriers and spaniels, or so large as the largest varieties ofhound or Newfoundland dog. And, certainly, no two wild animals of thefamily differ so widely in form and proportions as the Chinese pug andthe Italian greyhound, or the bulldog and the common greyhound. Theknown range of variation is, therefore, more than enough for thederivation of all the forms of Dogs, Wolves, and Foxes from a commonancestor. Again, it is objected that the Pouter or the Fan-tail pigeon cannot befurther developed in the same direction. Variation seems to have reachedits limits in these birds. But so it has in nature. The Fan-tail has notonly more tail feathers than any of the three hundred and forty existingspecies of pigeons, but more than any of the eight thousand knownspecies of birds. There is, of course, some limit to the number offeathers of which a tail useful for flight can consist, and in theFan-tail we have probably reached that limit. Many birds have theoesophagus or the skin of the neck more or less dilatable, but in noknown bird is it so dilatable as in the Pouter pigeon. Here again thepossible limit, compatible with a healthy existence, has probably beenreached. In like manner the differences in the size and form of the beakin the various breeds of the domestic Pigeon, is greater than thatbetween the extreme forms of beak in the various genera and sub-familiesof the whole Pigeon tribe. From these facts, and many others of the samenature, we may fairly infer, that if rigid selection were applied to anyorgan, we could in a comparatively short time produce a much greateramount of change than that which occurs between species and species in astate of nature, since the differences which we do produce are oftencomparable with those which exist between distinct genera or distinctfamilies. The facts adduced by the writer of the article referred to, ofthe definite limits to variability in certain directions in domesticatedanimals, are, therefore, no objection whatever to the view, that all themodifications which exist in nature have been produced by theaccumulation, by natural selection, of small and useful variations, since those very modifications have equally definite and very similarlimits. _Objection to the Argument from Classification. _ To another of this writer's objections--that by Professor Thomson'scalculations the sun can only have existed in a solid state 500, 000, 000of years, and that therefore _time_ would not suffice for the slowprocess of development of all living organisms--it is hardly necessaryto reply, as it cannot be seriously contended, even if this calculationhas claims to approximate accuracy, that the process of change anddevelopment may not have been sufficiently rapid to have occurred withinthat period. His objection to the Classification argument is, however, more plausible. The uncertainty of opinion among Naturalists as to whichare species and which varieties, is one of Mr. Darwin's very strongarguments that these two names cannot belong to things quite distinct innature and origin. The Reviewer says that this argument is of no weight, because the works of man present exactly the same phenomena; and heinstances patent inventions, and the excessive difficulty of determiningwhether they are new or old. I accept the analogy though it is a veryimperfect one, and maintain that such as it is, it is all in favour ofMr. Darwin's views. For are not all inventions of the same kind directlyaffiliated to a common ancestor? Are not improved Steam Engines orClocks the lineal descendants of some existing Steam Engine or Clock? Isthere ever a new Creation in Art or Science any more than in Nature? Didever patentee absolutely originate any complete and entire invention, noportion of which was derived from anything that had been made ordescribed before? It is therefore clear that the difficulty ofdistinguishing the various classes of inventions which claim to be new, is of the same nature as the difficulty of distinguishing varieties andspecies, because neither are absolute new creations, but both are alikedescendants of pre-existing forms, from which and from each other theydiffer by varying and often imperceptible degrees. It appears, then, that however plausible this writer's objections may seem, whenever hedescends from generalities to any specific statement, his supposeddifficulties turn out to be in reality strongly confirmatory of Mr. Darwin's view. _The "Times, " on Natural Selection. _ The extraordinary misconception of the whole subject by popular writersand reviewers, is well shown by an article which appeared in the _Times_newspaper on "The Reign of Law. " Alluding to the supposed economy ofnature, in the adaptation of each species to its own place and itsspecial use, the reviewer remarks: "To this universal law of thegreatest economy, the law of natural selection stands in directantagonism as the law of 'greatest possible waste' of time and ofcreative power. To conceive a duck with webbed feet and a spoon-shapedbill, living by suction, to pass naturally into a gull with webbed feetand a knife-like bill, living on flesh, in the longest possible time andin the most laborious possible way, we may conceive it to pass from theone to the other state by natural selection. The battle of life theducks will have to fight will increase in peril continually as theycease (with the change of their bill) to be ducks, and attain a_maximum_ of danger in the condition in which they begin to be gulls;and ages must elapse and whole generations must perish, and countlessgenerations of the one species be created and sacrificed, to arrive atone single pair of the other. " In this passage the theory of natural selection is so absurdlymisrepresented that it would be amusing, did we not consider themisleading effect likely to be produced by this kind of teaching in sopopular a journal. It is assumed that the duck and the gull areessential parts of nature, each well fitted for its place, and that ifone had been produced from the other by a gradual metamorphosis, theintermediate forms would have been useless, unmeaning, and unfitted forany place, in the system of the universe. Now, this idea can only existin a mind ignorant of the very foundation and essence of the theory ofnatural selection, which is, the preservation of _useful_ variationsonly, or, as has been well expressed, in other words, the "survival ofthe fittest. " Every intermediate form which could possibly have arisenduring the transition from the duck to the gull, so far from having anunusually severe battle to fight for existence, or incurring any"_maximum_ of danger, " would necessarily have been as accuratelyadjusted to the rest of nature, and as well fitted to maintain and toenjoy its existence, as the duck or the gull actually are. If it werenot so, it never could have been produced under the law of naturalselection. _Intermediate or generalized Forms of extinct Animals, an indication ofTransmutation or Development. _ The misconception of this writer illustrates another point veryfrequently overlooked. It is an essential part of Mr. Darwin's theory, that one existing animal has not been derived from any other existinganimal, but that both are the descendants of a common ancestor, whichwas at once different from either, but, in essential characters, intermediate between them both. The illustration of the duck and thegull is therefore misleading; one of these birds has not been derivedfrom the other, but both from a common ancestor. This is not a meresupposition invented to support the theory of natural selection, but isfounded on a variety of indisputable facts. As we go back into pasttime, and meet with the fossil remains of more and more ancient races ofextinct animals, we find that many of them actually are intermediatebetween distinct groups of existing animals. Professor Owen continuallydwells on this fact: he says in his "Palæontology, " p. 284: "A moregeneralized vertebrate structure is illustrated, in the extinctreptiles, by the affinities to ganoid fishes, shown by Ganocephala, Labyrinthodontia, and Icthyopterygia; by the affinities of thePterosauria to Birds, and by the approximation of the Dinosauria toMammals. (These have been recently shown by Professor Huxley to havemore affinity to Birds. ) It is manifested by the combination of moderncrocodilian, chelonian, and lacertian characters in the Cryptodontiaand the Dicnyodontia, and by the combined lacertian and crocodiliancharacters in the Thecodontia and Sauropterygia. " In the same work hetells us that, "the Anoplotherium, in several important charactersresembled the embryo Ruminant, but retained throughout life those marksof adhesion to a generalized mammalian type;"--and assures us that hehas "never omitted a proper opportunity for impressing the results ofobservations showing the more generalized structures of extinct ascompared with the more specialized forms of recent animals. " Modernpalæontologists have discovered hundreds of examples of these moregeneralized or ancestral types. In the time of Cuvier, the Ruminants andthe Pachyderms were looked upon as two of the most distinct orders ofanimals; but it is now demonstrated that there once existed a variety ofgenera and species, connecting by almost imperceptible grades suchwidely different animals as the pig and the camel. Among livingquadrupeds we can scarcely find a more isolated group than the genusEquus, comprising the horses, asses, and Zebras; but through manyspecies of Paloplotherium, Hippotherium, and Hipparion, and numbers ofextinct forms of Equus found in Europe, India, and America, an almostcomplete transition is established with the Eocene Anoplothorium andPaleotherium, which are also generalized or ancestral types of the Tapirand Rhinoceros. The recent researches of M. Gaudry in Greece havefurnished much new evidence of the same character. In the Miocene bedsof Pikermi he has discovered the group of the Simocyonidæ intermediatebetween bears and wolves; the genus Hyænictis which connects the hyænaswith the civets; the Ancylotherium, which is allied both to the extinctmastodon and to the living pangolin or scaly ant-eater; and theHelladotherium, which connects the now isolated giraffe with the deerand antelopes. Between reptiles and fishes an intermediate type has been found in theArchegosaurus of the Coal formation; while the Labyrinthodon of theTrias combined characters of the Batrachia with those of crocodiles, lizards, and ganoid fishes. Even birds, the most apparently isolated ofall living forms, and the most rarely preserved in a fossil state, havebeen shown to possess undoubted affinities with reptiles; and in theOolitic Archæopteryx, with its lengthened tail, feathered on each side, we have one of the connecting links from the side of birds; whileProfessor Huxley has recently shown that the entire order ofDinosaurians have remarkable affinities to birds, and that one of them, the Compsognathus, makes a nearer approach to bird organisation thandoes Archæopteryx to that of reptiles. Analogous facts to those occur in other classes of animals, asan example of which we have the authority of a distinguishedpaleontologist, M. Barande, quoted by Mr. Darwin, for the statement, that although the Palæozoic Invertebrata can certainly be classed underexisting groups, yet at this ancient period the groups were not sodistinctly separated from each other as they are now; while Mr. Scuddertells us, that some of the fossil insects discovered in the Coalformation of America offer characters intermediate between those ofexisting orders. Agassiz, again, insists strongly that the more ancientanimals resemble the embryonic forms of existing species; but as theembryos of distinct groups are known to resemble each other more thanthe adult animals (and in fact to be undistinguishable at a very earlyage), this is the same as saying that the ancient animals are exactlywhat, on Darwin's theory, the ancestors of existing animals ought to be;and this, it must be remembered, is the evidence of one of the strongestopponents of the theory of natural selection. _Conclusion. _ I have thus endeavoured to meet fairly, and to answer plainly, a few ofthe most common objections to the theory of natural selection, and Ihave done so in every case by referring to admitted facts and to logicaldeductions from those facts. As an indication and general summary of the line of argument I haveadopted, I here give a brief demonstration in a tabular form of theOrigin of Species by means of Natural Selection, referring for the_facts_ to Mr. Darwin's works, and to the pages in this volume, wherethey are more or less fully treated. _A Demonstration of the Origin of Species by Natural Selection_. ___________________________________________________________________ | | | |_PROVED FACTS_. |_NECESSARY CONSEQUENCES_ | | |(_afterwards taken as Proved | | |Facts_). | |_________________________________|_________________________________| | | | |RAPID INCREASE OF ORGANISMS, | | |pp. 29, 265; ("Origin |STRUGGLE FOR EXISTENCE, | |of Species, " p. 75, 5th Ed. ) |the deaths equalling the | | |births on the average, p. 30; | |TOTAL NUMBER OF INDIVIDUALS |("Origin of Species, " chap. | |STATIONARY, pp. 30, |III. ) | |266. | | |_________________________________|_________________________________| | | | |STRUGGLE FOR EXISTENCE. |SURVIVAL OF THE FITTEST, | | |or Natural Selection; meaning | |HEREDITY WITH VARIATION, |simply, that on the | |or general likeness with |whole those die who are | |individual differences of parents|least fitted to maintain their | |and offspring, pp. |existence; ("Origin of Species, " | |266, 287-291, 308; ("Origin |chap. IV. ) | |of Species, " chap. I. , II. , V. ) | | |_________________________________|_________________________________| | | | |SURVIVAL OF THE FITTEST. |CHANGES OF ORGANIC FORMS, | | |to keep them in harmony | |CHANGE OF EXTERNAL CONDITIONS, |with the Changed Conditions; | |universal and unceasing. --See |and as the changes | |"Lyell's |of conditions are permanent | |Principles of Geology. " |changes, in the sense | | |of not reverting back to | | |identical previous conditions, | | |the changes of organic | | |forms must be in the | | |same sense permanent, and | | |thus originate SPECIES. | |_________________________________|_________________________________| IX. THE DEVELOPMENT OF HUMAN RACES UNDER THE LAW OF NATURAL SELECTION. Among the most advanced students of man, there exists a wide differenceof opinion on some of the most vital questions respecting his nature andorigin. Anthropologists are now, indeed, pretty well agreed that man isnot a recent introduction into the earth. All who have studied thequestion, now admit that his antiquity is very great; and that, thoughwe have to some extent ascertained the minimum of time during which he_must_ have existed, we have made no approximation towards determiningthat far greater period during which he _may_ have, and probably _has_existed. We can with tolerable certainty affirm that man must haveinhabited the earth a thousand centuries ago, but we cannot assert thathe positively did not exist, or that there is any good evidence againsthis having existed, for a period of ten thousand centuries. We knowpositively, that he was contemporaneous with many now extinct animals, and has survived changes of the earth's surface fifty or a hundred timesgreater than any that have occurred during the historical period; but wecannot place any definite limit to the number of species he may haveoutlived, or to the amount of terrestrial change he may have witnessed. _Wide differences of opinion as to Man's Origin. _ But while on this question of man's antiquity there is a very generalagreement, --and all are waiting eagerly for fresh evidence to clear upthose points which all admit to be full of doubt, --on other, and notless obscure and difficult questions, a considerable amount of dogmatismis exhibited; doctrines are put forward as established truths, no doubtor hesitation is admitted, and it seems to be supposed that no furtherevidence is required, or that any new facts can modify our convictions. This is especially the case when we inquire, --Are the various formsunder which man now exists primitive, or derived from pre-existingforms; in other words, is man of one or many species? To this questionwe immediately obtain distinct answers diametrically opposed to eachother: the one party positively maintaining, that man is a _species_ andis essentially _one_--that all differences are but local and temporaryvariations, produced by the different physical and moral conditions bywhich he is surrounded; the other party maintaining with equalconfidence, that man is a genus of _many species_, each of which ispractically unchangeable, and has ever been as distinct, or even moredistinct, than we now behold them. This difference of opinion issomewhat remarkable, when we consider that both parties are wellacquainted with the subject; both use the same vast accumulation offacts; both reject those early traditions of mankind which profess togive an account of his origin; and both declare that they are seekingfearlessly after truth alone; yet each will persist in looking only atthe portion of truth on his own side of the question, and at the errorwhich is mingled with his opponent's doctrine. It is my wish to show howthe two opposing views can be combined, so as to eliminate the error andretain the truth in each, and it is by means of Mr. Darwin's celebratedtheory of "Natural Selection" that I hope to do this, and thus toharmonise the conflicting theories of modern anthropologists. Let us first see what each party has to say for itself. In favour of theunity of mankind it is argued, that there are no races withouttransitions to others; that every race exhibits within itself variationsof colour, of hair, of feature, and of form, to such a degree as tobridge over, to a large extent, the gap that separates it from otherraces. It is asserted that no race is homogeneous; that there is atendency to vary; that climate, food, and habits produce, and renderpermanent, physical peculiarities, which, though slight in the limitedperiods allowed to our observation, would, in the long ages during whichthe human race has existed, have sufficed to produce all the differencesthat now appear. It is further asserted that the advocates of theopposite theory do not agree among themselves; that some would makethree, some five, some fifty or a hundred and fifty species of man; somewould have had each species created in pairs, while others requirenations to have at once sprung into existence, and that there is nostability or consistency in any doctrine but that of one primitivestock. The advocates of the original diversity of man, on the other hand, havemuch to say for themselves. They argue that proofs of change in man havenever been brought forward except to the most trifling amount, whileevidence of his permanence meets us everywhere. The Portuguese andSpaniards, settled for two or three centuries in South America, retaintheir chief physical, mental, and moral characteristics; the Dutch boersat the Cape, and the descendants of the early Dutch settlers in theMoluccas, have not lost the features or the colour of the Germanicraces; the Jews, scattered over the world in the most diverse climates, retain the same characteristic lineaments everywhere; the Egyptiansculptures and paintings show us that, for at least 4000 or 5000 years, the strongly contrasted features of the Negro and the Semitic races haveremained altogether unchanged; while more recent discoveries prove, thatthe mound-builders of the Mississippi valley, and the dwellers onBrazilian mountains, had, even in the very infancy of the human race, some traces of the same peculiar and characteristic type of cranialformation that now distinguishes them. If we endeavour to decide impartially on the merits of this difficultcontroversy, judging solely by the evidence that each party has broughtforward, it certainly seems that the best of the argument is on theside of those who maintain the primitive diversity of man. Theiropponents have not been able to refute the permanence of existing racesas far back as we can trace them, and have failed to show, in a singlecase, that at any former epoch the well marked varieties of mankindapproximated more closely than they do at the present day. At the sametime this is but negative evidence. A condition of immobility for fouror five thousand years, does not preclude an advance at an earlierepoch, and--if we can show that there are causes in nature which wouldcheck any further physical change when certain conditions werefulfilled--does not even render such an advance improbable, if there areany general arguments to be adduced in its favour. Such a cause, Ibelieve, does exist; and I shall now endeavour to point out its natureand its mode of operation. _Outline of the Theory of Natural Selection. _ In order to make my argument intelligible, it is necessary for me toexplain very briefly the theory of "Natural Selection" promulgated byMr. Darwin, and the power which it possesses of modifying the forms ofanimals and plants. The grand feature in the multiplication of organiclife is, that close general resemblance is combined with more or lessindividual variation. The child resembles its parents or ancestors moreor less closely in all its peculiarities, deformities, or beauties; itresembles them in general more than it does any other individuals; yetchildren of the same parents are not all alike, and it often happensthat they differ very considerably from their parents and from eachother. This is equally true, of man, of all animals, and of all plants. Moreover, it is found that individuals do not differ from their parentsin certain particulars only, while in all others they are exactduplicates of them. They differ from them and from each other, in everyparticular: in form, in size, in colour; in the structure of internal aswell as of external organs; in those subtle peculiarities which producedifferences of constitution, as well as in those still more subtle oneswhich lead to modifications of mind and character. In other words, inevery possible way, in every organ and in every function, individuals ofthe same stock vary. Now, health, strength, and long life, are the results of a harmonybetween the individual and the universe that surrounds it. Let ussuppose that at any given moment this harmony is perfect. A certainanimal is exactly fitted to secure its prey, to escape from its enemies, to resist the inclemencies of the seasons, and to rear a numerous andhealthy offspring. But a change now takes place. A series of coldwinters, for instance, come on, making food scarce, and bringing animmigration of some other animals to compete with the former inhabitantsof the district. The new immigrant is swift of foot, and surpasses itsrivals in the pursuit of game; the winter nights are colder, and requirea thicker fur as a protection, and more nourishing food to keep up theheat of the system. Our supposed perfect animal is no longer in harmonywith its universe; it is in danger of dying of cold or of starvation. But the animal varies in its offspring. Some of these are swifter thanothers--they still manage to catch food enough; some are hardier andmore thickly furred--they manage in the cold nights to keep warm enough;the slow, the weak, and the thinly clad soon die off. Again and again, in each succeeding generation, the same thing takes place. By thisnatural process, which is so inevitable that it cannot be conceived notto act, those best adapted to live, live; those least adapted, die. Itis sometimes said that we have no direct evidence of the action of thisselecting power in nature. But it seems to me we have better evidencethan even direct observation would be, because it is more universal, viz. , the evidence of necessity. It must be so; for, as all wild animalsincrease in a geometrical ratio, while their actual numbers remain onthe average stationary, it follows, that as many die annually as areborn. If, therefore, we deny natural selection, it can only be byasserting that, in such a case as I have supposed, the strong, thehealthy, the swift, the well clad, the well organised animals in everyrespect, have no advantage over, --do not on the average live longerthan, the weak, the unhealthy, the slow, the ill-clad, and theimperfectly organised individuals; and this no sane man has yet beenfound hardy enough to assert. But this is not all; for the offspring onthe average resemble their parents, and the selected portion of eachsucceeding generation will therefore be stronger, swifter, and morethickly furred than the last; and if this process goes on for thousandsof generations, our animal will have again become thoroughly in harmonywith the new conditions in which it is placed. But it will now be adifferent creature. It will be not only swifter and stronger, and morefurry, it will also probably have changed in colour, in form, perhapshave acquired a longer tail, or differently shaped ears; for it is anascertained fact, that when one part of an animal is modified, someother parts almost always change, as it were in sympathy with it. Mr. Darwin calls this "correlation of growth, " and gives as instances, thathairless dogs have imperfect teeth; white cats, when blue-eyed, aredeaf; small feet accompany short beaks in pigeons; and other equallyinteresting cases. Grant, therefore, the premises: 1st. That peculiarities of every kindare more or less hereditary. 2nd. That the offspring of every animalvary more or less in all parts of their organization. 3rd. Thatthe universe in which these animals live, is not absolutelyinvariable;--none of which propositions can be denied; and thenconsider, that the animals in any country (those at least which are notdying out) must at each successive period be brought into harmony withthe surrounding conditions; and we have all the elements for a change ofform and structure in the animals, keeping exact pace with changes ofwhatever nature in the surrounding universe. Such changes must be slow, for the changes in the universe are very slow; but just as these slowchanges become important, when we look at results after long periods ofaction, as we do when we perceive the alterations of the earth's surfaceduring geological epochs; so the parallel changes in animal form becomemore and more striking, in proportion as the time they have been goingon is great; as we see when we compare our living animals with thosewhich we disentomb from each successively older geological formation. This is, briefly, the theory of "natural selection, " which explains thechanges in the organic world as being parallel with, and in partdependent on, those in the inorganic. What we now have to inquireis, --Can this theory be applied in any way to the question of the originof the races of man? or is there anything in human nature that takes himout of the category of those organic existences, over whose successivemutations it has had such powerful sway? _Different effects of Natural Selection on Animals and on Man. _ In order to answer these questions, we must consider why it is that"natural selection" acts so powerfully upon animals; and we shall, Ibelieve, find, that its effect depends mainly upon their self-dependenceand individual isolation. A slight injury, a temporary illness, willoften end in death, because it leaves the individual powerless againstits enemies. If an herbivorous animal is a little sick and has not fedwell for a day or two, and the herd is then pursued by a beast of prey, our poor invalid inevitably falls a victim. So, in a carnivorous animal, the least deficiency of vigour prevents its capturing food, and it soondies of starvation. There is, as a general rule, no mutual assistancebetween adults, which enables them to tide over a period of sickness. Neither is there any division of labour; each must fulfil _all_ theconditions of its existence, and, therefore, "natural selection" keepsall up to a pretty uniform standard. But in man, as we now behold him, this is different. He is social andsympathetic. In the rudest tribes the sick are assisted, at least withfood; less robust health and vigour than the average does not entaildeath. Neither does the want of perfect limbs, or other organs, producethe same effects as among animals. Some division of labour takes place;the swiftest hunt, the less active fish, or gather fruits; food is, tosome extent, exchanged or divided. The action of natural selection istherefore checked; the weaker, the dwarfish, those of less active limbs, or less piercing eyesight, do not suffer the extreme penalty which fallsupon animals so defective. In proportion as these physical characteristics become of lessimportance, mental and moral qualities will have increasing influence onthe well-being of the race. Capacity for acting in concert forprotection, and for the acquisition of food and shelter; sympathy, whichleads all in turn to assist each other; the sense of right, which checksdepredations upon our fellows; the smaller development of the combativeand destructive propensities; self-restraint in present appetites; andthat intelligent foresight which prepares for the future, are allqualities, that from their earliest appearance must have been for thebenefit of each community, and would, therefore, have become thesubjects of "natural selection. " For it is evident that such qualitieswould be for the well-being of man; would guard him against externalenemies, against internal dissensions, and against the effects ofinclement seasons and impending famine, more surely than could anymerely physical modification. Tribes in which such mental and moralqualities were predominant, would therefore have an advantage in thestruggle for existence over other tribes in which they were lessdeveloped, would live and maintain their numbers, while the others woulddecrease and finally succumb. Again, when any slow changes of physical geography, or of climate, makeit necessary for an animal to alter its food, its clothing, or itsweapons, it can only do so by the occurrence of a corresponding changein its own bodily structure and internal organization. If a larger ormore powerful beast is to be captured and devoured, as when acarnivorous animal which has hitherto preyed on antelopes is obligedfrom their decreasing numbers to attack buffaloes, it is only thestrongest who can hold, --those with most powerful claws, and formidablecanine teeth, that can struggle with and overcome such an animal. Natural selection immediately comes into play, and by its action theseorgans gradually become adapted to their new requirements. But man, under similar circumstances, does not require longer nails or teeth, greater bodily strength or swiftness. He makes sharper spears, or abetter bow, or he constructs a cunning pitfall, or combines in a huntingparty to circumvent his new prey. The capacities which enable him to dothis are what he requires to be strengthened, and these will, therefore, be gradually modified by "natural selection, " while the form andstructure of his body will remain unchanged. So, when a glacial epochcomes on, some animals must acquire warmer fur, or a covering of fat, orelse die of cold. Those best clothed by nature are, therefore, preservedby natural selection. Man, under the same circumstances, will makehimself warmer clothing, and build better houses; and the necessity ofdoing this will react upon his mental organization and socialcondition--will advance them while his natural body remains naked asbefore. When the accustomed food of some animal becomes scarce or totally fails, it can only exist by becoming adapted to a new kind of food, a foodperhaps less nourishing and less digestible. "Natural selection" willnow act upon the stomach and intestines, and all their individualvariations will be taken advantage of, to modify the race into harmonywith its new food. In many cases, however, it is probable that thiscannot be done. The internal organs may not vary quick enough, and thenthe animal will decrease in numbers, and finally become extinct. Butman guards himself from such accidents by superintending and guiding theoperations of nature. He plants the seed of his most agreeable food, andthus procures a supply, independent of the accidents of varying seasonsor natural extinction. He domesticates animals, which serve him eitherto capture food or for food itself, and thus, changes of any greatextent in his teeth or digestive organs are rendered unnecessary. Man, too, has everywhere the use of fire, and by its means can renderpalatable a variety of animal and vegetable substances, which he couldhardly otherwise make use of; and thus obtains for himself a supply offood far more varied and abundant than that which any animal cancommand. Thus man, by the mere capacity of clothing himself, and making weaponsand tools, has taken away from nature that power of slowly butpermanently changing the external form and structure, in accordance withchanges in the external world, which she exercises over all otheranimals. As the competing races by which they are surrounded, theclimate, the vegetation, or the animals which serve them for food, areslowly changing, they must undergo a corresponding change in theirstructure, habits, and constitution, to keep them in harmony with thenew conditions--to enable them to live and maintain their numbers. Butman does this by means of his intellect alone, the variations of whichenable him, with an unchanged body, still to keep in harmony with thechanging universe. There is one point, however, in which nature will still act upon him asit does on animals, and, to some extent, modify his external characters. Mr. Darwin has shown, that the colour of the skin is correlated withconstitutional peculiarities both in vegetables and animals, so thatliability to certain diseases or freedom from them is often accompaniedby marked external characters. Now, there is every reason to believethat this has acted, and, to some extent, may still continue to act, onman. In localities where certain diseases are prevalent, thoseindividuals of savage races which were subject to them would rapidly dieoff; while those who were constitutionally free from the disease wouldsurvive, and form the progenitors of a new race. These favouredindividuals would probably be distinguished by peculiarities of_colour_, with which again peculiarities in the texture or the abundanceof _hair_ seem to be correlated, and thus may have been brought aboutthose racial differences of colour, which seem to have no relation tomere temperature or other obvious peculiarities of climate. From the time, therefore, when the social and sympathetic feelings cameinto active operation, and the intellectual and moral faculties becamefairly developed, man would cease to be influenced by "naturalselection" in his physical form and structure. As an animal he wouldremain almost stationary, the changes of the surrounding universeceasing to produce in him that powerful modifying effect which theyexercise over other parts of the organic world. But from the momentthat the form of his body became stationary, his mind would becomesubject to those very influences from which his body had escaped; everyslight variation in his mental and moral nature which should enable himbetter to guard against adverse circumstances, and combine for mutualcomfort and protection, would be preserved and accumulated; the betterand higher specimens of our race would therefore increase and spread, the lower and more brutal would give way and successively die out, andthat rapid advancement of mental organization would occur, which hasraised the very lowest races of man so far above the brutes (althoughdiffering so little from some of them in physical structure), and, inconjunction with scarcely perceptible modifications of form, hasdeveloped the wonderful intellect of the European races. _Influence of external Nature in the development of the Human Mind. _ But from the time when this mental and moral advance commenced, andman's physical character became fixed and almost immutable, a new seriesof causes would come into action, and take part in his mental growth. The diverse aspects of nature would now make themselves felt, andprofoundly influence the character of the primitive man. When the power that had hitherto modified the body had its actiontransferred to the mind, then races would advance and become improved, merely by the harsh discipline of a sterile soil and inclement seasons. Under their influence, a hardier, a more provident, and a more socialrace would be developed, than in those regions where the earth producesa perennial supply of vegetable food, and where neither foresight noringenuity are required to prepare for the rigours of winter. And is itnot the fact that in all ages, and in every quarter of the globe, theinhabitants of temperate have been superior to those of hottercountries? All the great invasions and displacements of races have beenfrom North to South, rather than the reverse; and we have no record ofthere ever having existed, any more than there exists to-day, a solitaryinstance of an indigenous inter-tropical civilization. The Mexicancivilization and government came from the North, and, as well as thePeruvian, was established, not in the rich tropical plains, but on thelofty and sterile plateaux of the Andes. The religion and civilizationof Ceylon were introduced from North India; the successive conquerors ofthe Indian peninsula came from the North-west; the northern Mongolsconquered the more Southern Chinese; and it was the bold and adventuroustribes of the North that overran and infused new life into SouthernEurope. _Extinction of Lower Races. _ It is the same great law of "the preservation of favoured races in thestruggle for life, " which leads to the inevitable extinction of allthose low and mentally undeveloped populations with which Europeans comein contact. The red Indian in North America, and in Brazil; theTasmanian, Australian, and New Zealander in the southern hemisphere, dieout, not from any one special cause, but from the inevitable effects ofan unequal mental and physical struggle. The intellectual and moral, aswell as the physical, qualities of the European are superior; the samepowers and capacities which have made him rise in a few centuries fromthe condition of the wandering savage with a scanty and stationarypopulation, to his present state of culture and advancement, with agreater average longevity, a greater average strength, and a capacity ofmore rapid increase, --enable him when in contact with the savage man, toconquer in the struggle for existence, and to increase at his expense, just as the better adapted, increase at the expense of the less adaptedvarieties in the animal and vegetable kingdoms, --just as the weeds ofEurope overrun North America and Australia, extinguishing nativeproductions by the inherent vigour of their organization, and by theirgreater capacity for existence and multiplication. _The Origin of the Races of Man. _ If these views are correct; if in proportion as man's social, moral, andintellectual faculties became developed, his physical structure wouldcease to be affected by the operation of "natural selection, " we have amost important clue to the origin of races. For it will follow, thatthose great modifications of structure and of external form, whichresulted in the development of man out of some lower type of animal, must have occurred before his intellect had raised him above thecondition of the brutes, at a period when he was gregarious, butscarcely social, with a mind perceptive but not reflective, ere anysense of _right_ or feelings of _sympathy_ had been developed in him. Hewould be still subject, like the rest of the organic world, to theaction of "natural selection, " which would retain his physical form andconstitution in harmony with the surrounding universe. He was probablyat a very early period a dominant race, spreading widely over the warmerregions of the earth as it then existed, and in agreement with what wesee in the case of other dominant species, gradually becoming modifiedin accordance with local conditions. As he ranged farther from hisoriginal home, and became exposed to greater extremes of climate, togreater changes of food, and had to contend with new enemies, organicand inorganic, slight useful variations in his constitution would beselected and rendered permanent, and would, on the principle of"correlation of growth, " be accompanied by corresponding externalphysical changes. Thus might have arisen those striking characteristicsand special modifications which still distinguish the chief races ofmankind. The red, black, yellow, or blushing white skin; the straight, the curly, the woolly hair; the scanty or abundant beard; the straightor oblique eyes; the various forms of the pelvis, the cranium, and otherparts of the skeleton. But while these changes had been going on, his mental development had, from some unknown cause, greatly advanced, and had now reached thatcondition in which it began powerfully to influence his whole existence, and would therefore become subject to the irresistible action of"natural selection. " This action would quickly give the ascendency tomind: speech would probably now be first developed, leading to a stillfurther advance of the mental faculties; and from that moment man, asregards the form and structure of most parts of his body, would remainalmost stationary. The art of making weapons, division of labour, anticipation of the future, restraint of the appetites, moral, social, and sympathetic feelings, would now have a preponderating influence onhis well being, and would therefore be that part of his nature on which"natural selection" would most powerfully act; and we should thus haveexplained that wonderful persistence of mere physical characteristics, which is the stumbling-block of those who advocate the unity of mankind. We are now, therefore, enabled to harmonise the conflicting views ofanthropologists on this subject. Man may have been, indeed I believemust have been, once a homogeneous race; but it was at a period of whichwe have as yet discovered no remains, at a period so remote in hishistory, that he had not yet acquired that wonderfully developed brain, the organ of the mind, which now, even in his lowest examples, raiseshim far above the highest brutes;--at a period when he had the form buthardly the nature of man, when he neither possessed human speech, northose sympathetic and moral feelings which in a greater or less degreeeverywhere now distinguish the race. Just in proportion as these trulyhuman faculties became developed in him, would his physical featuresbecome fixed and permanent, because the latter would be of lessimportance to his well being; he would be kept in harmony with theslowly changing universe around him, by an advance in mind, rather thanby a change in body. If, therefore, we are of opinion that he was notreally man till these higher faculties were fully developed, we mayfairly assert that there were many originally distinct races of men;while, if we think that a being closely resembling us in form andstructure, but with mental faculties scarcely raised above the brute, must still be considered to have been human, we are fully entitled tomaintain the common origin of all mankind. _The Bearing of these Views on the Antiquity of Man. _ These considerations, it will be seen, enable us to place the origin ofman at a much more remote geological epoch than has yet been thoughtpossible. He may even have lived in the Miocene or Eocene period, whennot a single mammal was identical in form with any existing species. For, in the long series of ages during which these primeval animals werebeing slowly changed into the species which now inhabit the earth, thepower which acted to modify them would only affect the mentalorganization of man. His brain alone would have increased in size andcomplexity, and his cranium have undergone corresponding changes ofform, while the whole structure of lower animals was being changed. Thiswill enable us to understand how the fossil crania of Denise and Engisagree so closely with existing forms, although they undoubtedly existedin company with large mammalia now extinct. The Neanderthal skull may bea specimen of one of the lowest races then existing, just as theAustralians are the lowest of our modern epoch. We have no reason tosuppose that mind and brain and skull modification, could go on quickerthan that of the other parts of the organization; and we must thereforelook back very far in the past, to find man in that early condition inwhich his mind was not sufficiently developed, to remove his body fromthe modifying influence of external conditions and the cumulative actionof "natural selection. " I believe, therefore, that there is no _àpriori_ reason against our finding the remains of man or his works inthe tertiary deposits. The absence of all such remains in the Europeanbeds of this age has little weight, because, as we go further back intime, it is natural to suppose that man's distribution over the surfaceof the earth was less universal than at present. Besides, Europe was in a great measure submerged during the tertiaryepoch; and though its scattered islands may have been uninhabited byman, it by no means follows that he did not at the same time exist inwarm or tropical continents. If geologists can point out to us the mostextensive land in the warmer regions of the earth, which has not beensubmerged since Eocene or Miocene times, it is there that we may expectto find some traces of the very early progenitors of man. It is therethat we may trace back the gradually decreasing brain of former races, till we come to a time when the body also begins materially to differ. Then we shall have reached the starting point of the human family. Before that period, he had not mind enough to preserve his body fromchange, and would, therefore, have been subject to the samecomparatively rapid modifications of form as the other mammalia. _Their Bearing on the Dignity and Supremacy of Man. _ If the views I have here endeavoured to sustain have any foundation, they give us a new argument for placing man apart, as not only the headand culminating point of the grand series of organic nature, but as insome degree a new and distinct order of being. From those infinitelyremote ages, when the first rudiments of organic life appeared upon theearth, every plant, and every animal has been subject to one great lawof physical change. As the earth has gone through its grand cycles ofgeological, climatal, and organic progress, every form of life has beensubject to its irresistible action, and has been continually, butimperceptibly moulded into such new shapes as would preserve theirharmony with the ever-changing universe. No living thing could escapethis law of its being; none (except, perhaps, the simplest and mostrudimentary organisms), could remain unchanged and live, amid theuniversal change around it. At length, however, there came into existence a being in whom thatsubtle force we term _mind_, became of greater importance than his merebodily structure. Though with a naked and unprotected body, _this_ gavehim clothing against the varying inclemencies of the seasons. Thoughunable to compete with the deer in swiftness, or with the wild bull instrength, _this_ gave him weapons with which to capture or overcomeboth. Though less capable than most other animals of living on the herbsand the fruits that unaided nature supplies, this wonderful facultytaught him to govern and direct nature to his own benefit, and make herproduce food for him, when and where he pleased. From the moment whenthe first skin was used as a covering, when the first rude spear wasformed to assist in the chase, when fire was first used to cook hisfood, when the first seed was sown or shoot planted, a grand revolutionwas effected in nature, a revolution which in all the previous ages ofthe earth's history had had no parallel, for a being had arisen who wasno longer necessarily subject to change with the changing universe--abeing who was in some degree superior to nature, inasmuch as he knew howto control and regulate her action, and could keep himself in harmonywith her, not by a change in body, but by an advance of mind. Here, then, we see the true grandeur and dignity of man. On this view ofhis special attributes, we may admit, that even those who claim for hima position as an order, a class, or a sub-kingdom by himself, have someshow of reason on their side. He is, indeed, a being apart, since he isnot influenced by the great laws which irresistibly modify all otherorganic beings. Nay more; this victory which he has gained for himself, gives him a directing influence over other existences. Man has not onlyescaped "natural selection" himself, but he is actually able to takeaway some of that power from nature which before his appearance sheuniversally exercised. We can anticipate the time when the earth willproduce only cultivated plants and domestic animals; when man'sselection shall have supplanted "natural selection;" and when the oceanwill be the only domain in which that power can be exerted, which forcountless cycles of ages ruled supreme over all the earth. _Their Bearing on the future Development of Man. _ We now find ourselves enabled to answer those who maintain, that if Mr. Darwin's theory of the Origin of Species is true, man too must change inform, and become developed into some other animal as different from hispresent self as he is from the Gorilla or the Chimpanzee; and whospeculate on what this form is likely to be. But it is evident that suchwill not be the case; for no change of conditions is conceivable, whichwill render any important alteration of his form and organization souniversally useful and necessary to him, as to give those possessing italways the best chance of surviving, and thus lead to the developmentof a new species, genus, or higher group of man. On the other hand, weknow that far greater changes of conditions and of his entireenvironment have been undergone by man, than any other highly organizedanimal could survive unchanged, and have been met by mental, notcorporeal adaptation. The difference of habits, of food, clothing, weapons, and enemies, between savage and civilized man, is enormous. Difference in bodily form and structure there is practically none, except a slightly increased size of brain, corresponding to his highermental development. We have every reason to believe, then, that man may have existed and maycontinue to exist, through a series of geological periods which shallsee all other forms of animal life again and again changed; while hehimself remains unchanged, except in the two particulars alreadyspecified--the head and face, as immediately connected with the organ ofthe mind and as being the medium of expressing the most refined emotionsof his nature, --and to a slight extent in colour, hair, and proportions, so far as they are correlated with constitutional resistance to disease. _Summary. _ Briefly to recapitulate the argument;--in two distinct ways has manescaped the influence of those laws which have produced unceasing changein the animal world. 1. By his superior intellect he is enabled toprovide himself with clothing and weapons, and by cultivating the soilto obtain a constant supply of congenial food. This renders itunnecessary for his body, like those of the lower animals, to bemodified in accordance with changing conditions--to gain a warmernatural covering, to acquire more powerful teeth or claws, or to becomeadapted to obtain and digest new kinds of food, as circumstances mayrequire. 2. By his superior sympathetic and moral feelings, he becomesfitted for the social state; he ceases to plunder the weak and helplessof his tribe; he shares the game which he has caught with less active orless fortunate hunters, or exchanges it for weapons which even the weakor the deformed can fashion; he saves the sick and wounded from death;and thus the power which leads to the rigid destruction of all animalswho cannot in every respect help themselves, is prevented from acting onhim. This power is "natural selection;" and, as by no other means can it beshown, that individual variations can ever become accumulated andrendered permanent so as to form well-marked races, it follows that thedifferences which now separate mankind from other animals, must havebeen produced before he became possessed of a human intellect or humansympathies. This view also renders possible, or even requires, theexistence of man at a comparatively remote geological epoch. For, duringthe long periods in which other animals have been undergoingmodification in their whole structure, to such an amount as toconstitute distinct genera and families, man's _body_ will haveremained generically, or even specifically, the same, while his _head_and _brain_ alone will have undergone modification equal to theirs. Wecan thus understand how it is that, judging from the head and brain, Professor Owen places man in a distinct sub-class of mammalia, while asregards the bony structure of his body, there is the closest anatomicalresemblance to the anthropoid apes, "every tooth, every bone, strictlyhomologous--which makes the determination of the difference between_Homo_ and _Pithecus_ the anatomist's difficulty. " The present theoryfully recognises and accounts for these facts; and we may perhaps claimas corroborative of its truth, that it neither requires us to depreciatethe intellectual chasm which separates man from the apes, nor refusesfull recognition of the striking resemblances to them, which exist inother parts of his structure. _Conclusion. _ In concluding this brief sketch of a great subject, I would point outits bearing upon the future of the human race. If my conclusions arejust, it must inevitably follow that the higher--the more intellectualand moral--must displace the lower and more degraded races; and thepower of "natural selection, " still acting on his mental organization, must ever lead to the more perfect adaptation of man's higher facultiesto the conditions of surrounding nature, and to the exigencies of thesocial state. While his external form will probably ever remainunchanged, except in the development of that perfect beauty whichresults from a healthy and well organized body, refined and ennobled bythe highest intellectual faculties and sympathetic emotions, his mentalconstitution may continue to advance and improve, till the world isagain inhabited by a single nearly homogeneous race, no individual ofwhich will be inferior to the noblest specimens of existing humanity. Our progress towards such a result is very slow, but it still seems tobe a progress. We are just now living at an abnormal period of theworld's history, owing to the marvellous developments and vast practicalresults of science, having been given to societies too low morally andintellectually, to know how to make the best use of them, and to whomthey have consequently been curses as well as blessings. Among civilizednations at the present day, it does not seem possible for naturalselection to act in any way, so as to secure the permanent advancementof morality and intelligence; for it is indisputably the mediocre, ifnot the low, both as regards morality and intelligence, who succeed bestin life and multiply fastest. Yet there is undoubtedly an advance--onthe whole a steady and a permanent one--both in the influence on publicopinion of a high morality, and in the general desire for intellectualelevation; and as I cannot impute this in any way to "survival of thefittest, " I am forced to conclude that it is due, to the inherentprogressive power of those glorious qualities which raise us soimmeasurably above our fellow animals, and at the same time afford usthe surest proof that there are other and higher existences thanourselves, from whom these qualities may have been derived, and towardswhom we may be ever tending. X. THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN. Throughout this volume I have endeavoured to show, that the known lawsof variation, multiplication, and heredity, resulting in a "struggle forexistence" and the "survival of the fittest, " have probably sufficed toproduce all the varieties of structure, all the wonderful adaptations, all the beauty of form and of colour, that we see in the animal andvegetable kingdoms. To the best of my ability I have answered the mostobvious and the most often repeated objections to this theory, and have, I hope, added to its general strength, by showing how colour--one of thestrongholds of the advocates of special creation--may be, in almost allits modifications, accounted for by the combined influence of sexualselection and the need of protection. I have also endeavoured to show, how the same power which has modified animals has acted on man; andhave, I believe, proved that, as soon as the human intellect becamedeveloped above a certain low stage, man's body would cease to bematerially affected by natural selection, because the development of hismental faculties would render important modifications of its form andstructure unnecessary. It will, therefore, probably excite somesurprise among my readers, to find that I do not consider that allnature can be explained on the principles of which I am so ardent anadvocate; and that I am now myself going to state objections, and toplace limits, to the power of "natural selection. " I believe, however, that there are such limits; and that just as surely as we can trace theaction of natural laws in the development of organic forms, and canclearly conceive that fuller knowledge would enable us to follow step bystep the whole process of that development, so surely can we trace theaction of some unknown higher law, beyond and independent of all thoselaws of which we have any knowledge. We can trace this action more orless distinctly in many phenomena, the two most important of whichare--the origin of sensation or consciousness, and the development ofman from the lower animals. I shall first consider the latter difficultyas more immediately connected with the subjects discussed in thisvolume. _What Natural Selection can Not do. _ In considering the question of the development of man by known naturallaws, we must ever bear in mind the first principle of "naturalselection, " no less than of the general theory of evolution, that allchanges of form or structure, all increase in the size of an organ or inits complexity, all greater specialization or physiological division oflabour, can only be brought about, in as much as it is for the good ofthe being so modified. Mr. Darwin himself has taken care to impressupon us, that "natural selection" has no power to produce absoluteperfection but only relative perfection, no power to advance any beingmuch beyond his follow beings, but only just so much beyond them as toenable it to survive them in the struggle for existence. Still less hasit any power to produce modifications which are in any degree injuriousto its possessor, and Mr. Darwin frequently uses the strong expression, that a single case of this kind would be fatal to his theory. If, therefore, we find in man any characters, which all the evidence we canobtain goes to show would have been actually injurious to him on theirfirst appearance, they could not possibly have been produced by naturalselection. Neither could any specially developed organ have been soproduced if it had been merely useless to him, or if its use were notproportionate to its degree of development. Such cases as these wouldprove, that some other law, or some other power, than "naturalselection" had been at work. But if, further, we could see that thesevery modifications, though hurtful or useless at the time when theyfirst appeared, became in the highest degree useful at a much laterperiod, and are now essential to the full moral and intellectualdevelopment of human nature, we should then infer the action of mind, foreseeing the future and preparing for it, just as surely as we do, when we see the breeder set himself to work with the determination toproduce a definite improvement in some cultivated plant or domesticanimal. I would further remark that this enquiry is as thoroughlyscientific and legitimate as that into the origin of species itself. Itis an attempt to solve the inverse problem, to deduce the existence of anew power of a definite character, in order to account for facts whichaccording to the theory of natural selection ought not to happen. Suchproblems are well known to science, and the search after their solutionhas often led to the most brilliant results. In the case of man, thereare facts of the nature above alluded to, and in calling attention tothem, and in inferring a cause for them, I believe that I am as strictlywithin the bounds of scientific investigation as I have been in anyother portion of my work. _The Brain of the Savage shown to be Larger than he Needs it to be. _ _Size of Brain an important Element of Mental Power. _--The brain isuniversally admitted to be the organ of the mind; and it is almost asuniversally admitted, that size of brain is one of the most important ofthe elements which determine mental power or capacity. There seems to beno doubt that brains differ considerably in quality, as indicated bygreater or less complexity of the convolutions, quantity of grey matter, and perhaps unknown peculiarities of organization; but this differenceof quality seems merely to increase or diminish the influence ofquantity, not to neutralize it. Thus, all the most eminent modernwriters see an intimate connection between the diminished size of thebrain in the lower races of mankind, and their intellectualinferiority. The collections of Dr. J. B. Davis and Dr. Morton give thefollowing as the average internal capacity of the cranium in the chiefraces:--Teutonic family, 94 cubic inches; Esquimaux, 91 cubic inches;Negroes, 85 cubic inches; Australians and Tasmanians, 82 cubic inches;Bushmen, 77 cubic inches. These last numbers, however, are deduced fromcomparatively few specimens, and may be below the average, just as asmall number of Finns and Cossacks give 98 cubic inches, or considerablymore than that of the German races. It is evident, therefore, that theabsolute bulk of the brain is not necessarily much less in savage thanin civilised man, for Esquimaux skulls are known with a capacity of 113inches, or hardly less than the largest among Europeans. But what isstill more extraordinary, the few remains yet known of pre-historic mando not indicate any material diminution in the size of the brain case. ASwiss skull of the stone age, found in the lake dwelling of Meilen, corresponded exactly to that of a Swiss youth of the present day. Thecelebrated Neanderthal skull had a larger circumference than theaverage, and its capacity, indicating actual mass of brain, is estimatedto have been not less than 75 cubic inches, or nearly the average ofexisting Australian crania. The Engis skull, perhaps the oldest known, and which, according to Sir John Lubbock, "there seems no doubt wasreally contemporary with the mammoth and the cave bear, " is yet, according to Professor Huxley, "a fair average skull, which might havebelonged to a philosopher, or might have contained the thoughtlessbrains of a savage. " Of the cave men of Les Eyzies, who were undoubtedlycontemporary with the reindeer in the South of France, Professor PaulBroca says (in a paper read before the Congress of Pre-historicArchæology in 1868)--"The great capacity of the brain, the developmentof the frontal region, the fine elliptical form of the anterior part ofthe profile of the skull, are incontestible characteristics ofsuperiority, such as we are accustomed to meet with in civilised races;"yet the great breadth of the face, the enormous development of theascending ramus of the lower jaw, the extent and roughness of thesurfaces for the attachment of the muscles, especially of themasticators, and the extraordinary development of the ridge of thefemur, indicate enormous muscular power, and the habits of a savage andbrutal race. These facts might almost make us doubt whether the size of the brain isin any direct way an index of mental power, had we not the mostconclusive evidence that it is so, in the fact that, whenever an adultmale European has a skull less than nineteen inches in circumference, orhas less than sixty-five cubic inches of brain, he is invariablyidiotic. When we join with this the equally undisputed fact, that greatmen--those who combine acute perception with great reflective power, strong passions, and general energy of character, such as Napoleon, Cuvier, and O'Connell, have always heads far above the average size, wemust feel satisfied that volume of brain is one, and perhaps the mostimportant, measure of intellect; and this being the case, we cannot failto be struck with the apparent anomaly, that many of the lowest savagesshould have as much brains as average Europeans. The idea is suggestedof a surplusage of power; of an instrument beyond the needs of itspossessor. _Comparison of the Brains of Man and of Anthropoid Apes. _--In order todiscover if there is any foundation for this notion, let us compare thebrain of man with that of animals. The adult male Orang-utan is quite asbulky as a small sized man, while the Gorilla is considerably above theaverage size of man, as estimated by bulk and weight; yet the former hasa brain of only 28 cubic inches, the latter, one of 30, or, in thelargest specimen yet known, of 34œ cubic inches. We have seen that theaverage cranial capacity of the lowest savages is probably not less than_five-sixths_ of that of the highest civilized races, while the brain ofthe anthropoid apes scarcely amounts to _one-third_ of that of man, inboth cases taking the average; or the proportions may be more clearlyrepresented by the following figures--anthropoid apes, 10; savages, 26;civilized man, 32. But do these figures at all approximately representthe relative intellect of the three groups? Is the savage really nofarther removed from the philosopher, and so much removed from the ape, as these figures would indicate? In considering this question, we mustnot forget that the heads of savages vary in size, almost as much asthose of civilized Europeans. Thus, while the largest Teutonic skull inDr. Davis' collection is 112·4 cubic inches, there is an Araucanian of115·5, an Esquimaux of 113·1, a Marquesan of 11O·6, a Negro of 105·8, and even an Australian of 104·5 cubic inches. We may, therefore, fairlycompare the savage with the highest European on the one side, and withthe Orang, Chimpanzee, or Gorilla, on the other, and see whether thereis any relative proportion between brain and intellect. _Range of intellectual power in Man. _--First, let us consider what thiswonderful instrument, the brain, is capable of in its higherdevelopments. In Mr. Galton's interesting work on "Hereditary Genius, "he remarks on the enormous difference between the intellectual power andgrasp of the well-trained mathematician or man of science, and theaverage Englishman. The number of marks obtained by high wranglers, isoften more than thirty times as great as that of the men at the bottomof the honour list, who are still of fair mathematical ability; and itis the opinion of skilled examiners, that even this does not representthe full difference of intellectual power. If, now, we descend to thosesavage tribes who only count to three or five, and who find itimpossible to comprehend the addition of two and three without havingthe objects actually before them, we feel that the chasm between themand the good mathematician is so vast, that a thousand to one willprobably not fully express it. Yet we know that the mass of brain mightbe nearly the same in both, or might not differ in a greater proportionthan as 5 to 6; whence we may fairly infer that the savage possesses abrain capable, if cultivated and developed, of performing work of a kindand degree far beyond what he ever requires it to do. Again, let us consider the power of the higher or even the averagecivilized man, of forming abstract ideas, and carrying on more or lesscomplex trains of reasoning. Our languages are full of terms to expressabstract conceptions. Our business and our pleasures involve thecontinual foresight of many contingencies. Our law, our government, andour science, continually require us to reason through a variety ofcomplicated phenomena to the expected result. Even our games, such aschess, compel us to exercise all these faculties in a remarkable degree. Compare this with the savage languages, which contain no words forabstract conceptions; the utter want of foresight of the savage manbeyond his simplest necessities; his inability to combine, or tocompare, or to reason on any general subject that does not immediatelyappeal to his senses. So, in his moral and æsthetic faculties, thesavage has none of those wide sympathies with all nature, thoseconceptions of the infinite, of the good, of the sublime and beautiful, which are so largely developed in civilized man. Any considerabledevelopment of these would, in fact, be useless or even hurtful to him, since they would to some extent interfere with the supremacy of thoseperceptive and animal faculties on which his very existence oftendepends, in the severe struggle he has to carry on against nature andhis fellow-man. Yet the rudiments of all these powers and feelingsundoubtedly exist in him, since one or other of them frequently manifestthemselves in exceptional cases, or when some special circumstances callthem forth. Some tribes, such as the Santals, are remarkable for as purea love of truth as the most moral among civilized men. The Hindoo andthe Polynesian have a high artistic feeling, the first traces of whichare clearly visible in the rude drawings of the palæolithic men who werethe contemporaries in France of the Reindeer and the Mammoth. Instancesof unselfish love, of true gratitude, and of deep religious feeling, sometimes occur among most savage races. On the whole, then, we may conclude, that the general moral andintellectual development of the savage, is not less removed from that ofcivilized man than has been shown to be the case in the one departmentof mathematics; and from the fact that all the moral and intellectualfaculties do occasionally manifest themselves, we may fairly concludethat they are always latent, and that the large brain of the savage manis much beyond his actual requirements in the savage state. _Intellect of Savages and of Animals compared. _--Let us now compare theintellectual wants of the savage, and the actual amount of intellect heexhibits, with those of the higher animals. Such races as the AndamanIslanders, the Australians, and the Tasmanians, the Digger Indians ofNorth America, or the natives of Fuegia, pass their lives so as torequire the exercise of few faculties not possessed in an equal degreeby many animals. In the mode of capture of game or fish, they by nomeans surpass the ingenuity or forethought of the jaguar, who dropssaliva into the water, and seizes the fish as they come to eat it; or ofwolves and jackals, who hunt in packs; or of the fox, who buries hissurplus food till he requires it. The sentinels placed by antelopes andby monkeys, and the various modes of building adopted by field mice andbeavers, as well as the sleeping place of the orang-utan, and thetree-shelter of some of the African anthropoid apes, may well becompared with the amount of care and forethought bestowed by manysavages in similar circumstances. His possession of free and perfecthands, not required for locomotion, enable man to form and use weaponsand implements which are beyond the physical powers of brutes; buthaving done this, he certainly does not exhibit more mind in using themthan do many lower animals. What is there in the life of the savage, butthe satisfying of the cravings of appetite in the simplest and easiestway? What thoughts, ideas, or actions are there, that raise him manygrades above the elephant or the ape? Yet he possesses, as we have seen, a brain vastly superior to theirs in size and complexity; and this braingives him, in an undeveloped state, faculties which he never requires touse. And if this is true of existing savages, how much more true mustit have been of the men whose sole weapons were rudely chipped flints, and some of whom, we may fairly conclude, were lower than any existingrace; while the only evidence yet in our possession shows them to havehad brains fully as capacious as those of the average of the lowersavage races. We see, then, that whether we compare the savage with the higherdevelopments of man, or with the brutes around him, we are alike drivento the conclusion that in his large and well-developed brain hepossesses an organ quite disproportionate to his actual requirements--anorgan that seems prepared in advance, only to be fully utilized as heprogresses in civilization. A brain slightly larger than that of thegorilla would, according to the evidence before us, fully have sufficedfor the limited mental development of the savage; and we must thereforeadmit, that the large brain he actually possesses could never have beensolely developed by any of those laws of evolution, whose essence is, that they lead to a degree of organization exactly proportionate to thewants of each species, never beyond those wants--that no preparation canbe made for the future development of the race--that one part of thebody can never increase in size or complexity, except in strictco-ordination to the pressing wants of the whole. The brain ofpre-historic and of savage man seems to me to prove the existence ofsome power, distinct from that which has guided the development of thelower animals through their ever-varying forms of being. _The Use of the Hairy Covering of Mammalia. _ Let us now consider another point in man's organization, the bearing ofwhich has been almost entirely overlooked by writers on both sides ofthis question. One of the most general external characters of theterrestrial mammalia is the hairy covering of the body, which, wheneverthe skin is flexible, soft, and sensitive, forms a natural protectionagainst the severities of climate, and particularly against rain. Thatthis is its most important function, is well shown by the manner inwhich the hairs are disposed so as to carry off the water, by beinginvariably directed downwards from the most elevated parts of the body. Thus, on the under surface the hair is always less plentiful, and, inmany cases, the belly is almost bare. The hair lies downwards, on thelimbs of all walking mammals, from the shoulder to the toes, but in theorang-utan it is directed from the shoulder to the elbow, and again fromthe wrist to the elbow, in a reverse direction. This corresponds to thehabits of the animal, which, when resting, holds its long arms upwardsover its head, or clasping a branch above it, so that the rain wouldflow down both the arm and fore-arm to the long hair which meets at theelbow. In accordance with this principle, the hair is always longer ormore dense along the spine or middle of the back from the nape to thetail, often rising into a crest of hair or bristles on the ridge of theback. This character prevails through the entire series of the mammalia, from the marsupials to the quadrumana, and by this long persistence itmust have acquired such a powerful hereditary tendency, that we shouldexpect it to reappear continually even after it had been abolished byages of the most rigid selection; and we may feel sure that it nevercould have been completely abolished under the law of natural selection, unless it had become so positively injurious as to lead to the almostinvariable extinction of individuals possessing it. _The constant absence of Hair from certain parts of Man's Body aremarkable Phenomenon. _ In man the hairy covering of the body has almost totally disappeared, and, what is very remarkable, it has disappeared more completely fromthe back than from any other part of the body. Bearded and beardlessraces alike have the back smooth, and even when a considerable quantityof hair appears on the limbs and breast, the back, and especially thespinal region, is absolutely free, thus completely reversing thecharacteristics of all other mammalia. The Ainos of the Kurile Islandsand Japan are said to be a hairy race; but Mr. Bickmore, who saw some ofthem, and described them in a paper read before the EthnologicalSociety, gives no details as to where the hair was most abundant, merelystating generally, that "their chief peculiarity is their greatabundance of hair, not only on the head and face, but over the wholebody. " This might very well be said of any man who had hairy limbs andbreast, unless it was specially stated that his back was hairy, whichis not done in this case. The hairy family in Birmah have, indeed, hairon the back rather longer than on the breast, thus reproducing the truemammalian character, but they have still longer hair on the face, forehead, and inside the ears, which is quite abnormal; and the factthat their teeth are all very imperfect, shows that this is a case ofmonstrosity rather than one of true reversion to the ancestral type ofman before he lost his hairy covering. _Savage Man feels the Want of this Hairy Covering. _ We must now enquire if we have any evidence to show, or any reason tobelieve, that a hairy covering to the back would be in any degreehurtful to savage man, or to man in any stage of his progress from hislower animal form; and if it were merely useless, could it have been soentirely and completely removed as not to be continually reappearing inmixed races? Let us look to savage man for some light on these points. One of the most common habits of savages is to use some covering for theback and shoulders, even when they have none on any other part of thebody. The early voyagers observed with surprise, that the Tasmanians, both men and women, wore the kangaroo-skin, which was their onlycovering, not from any feeling of modesty, but over the shoulders tokeep the back dry and warm. A cloth over the shoulders was also thenational dress of the Maories. The Patagonians wear a cloak or mantleover the shoulders, and the Fuegians often wear a small piece of skin onthe back, laced on, and shifted from side to side as the wind blows. The Hottentots also wore a somewhat similar skin over the back, whichthey never removed, and in which they were buried. Even in the tropicsmost savages take precautions to keep their backs dry. The natives ofTimor use the leaf of a fan palm, carefully stitched up and folded, which they always carry with them, and which, held over the back, formsan admirable protection from the rain. Almost all the Malay races, aswell as the Indians of South America, make great palm-leaf hats, fourfeet or more across, which they use during their canoe voyages toprotect their bodies from heavy showers of rain; and they use smallerhats of the same kind when travelling by land. We find, then, that so far from there being any reason to believe that ahairy covering to the back could have been hurtful or even useless topre-historic man, the habits of modern savages indicate exactly theopposite view, as they evidently feel the want of it, and are obliged toprovide substitutes of various kinds. The perfectly erect posture ofman, may be supposed to have something to do with the disappearance ofthe hair from his body, while it remains on his head; but when walking, exposed to rain and wind, a man naturally stoops forwards, and thusexposes his back; and the undoubted fact, that most savages feel theeffects of cold and wet most severely in that part of the body, sufficiently demonstrates that the hair could not have ceased to growthere merely because it was useless, even if it were likely that acharacter so long persistent in the entire order of mammalia, could haveso completely disappeared, under the influence of so weak a selectivepower as a diminished usefulness. _Man's Naked Skin could not have been produced by Natural Selection. _ It seems to me, then, to be absolutely certain, that "Natural Selection"could not have produced man's hairless body by the accumulation ofvariations from a hairy ancestor. The evidence all goes to show thatsuch variations could not have been useful, but must, on the contrary, have been to some extent hurtful. If even, owing to an unknowncorrelation with other hurtful qualities, it had been abolished in theancestral tropical man, we cannot conceive that, as man spread intocolder climates, it should not have returned under the powerfulinfluence of reversion to such a long persistent ancestral type. But thevery foundation of such a supposition as this is untenable; for wecannot suppose that a character which, like hairiness, exists throughoutthe whole of the mammalia, can have become, in one form only, soconstantly correlated with an injurious character, as to lead to itspermanent suppression--a suppression so complete and effectual that itnever, or scarcely ever, reappears in mongrels of the most widelydifferent races of man. Two characters could hardly be wider apart, than the size anddevelopment of man's brain, and the distribution of hair upon thesurface of his body; yet they both lead us to the same conclusion--thatsome other power than Natural Selection has been engaged in hisproduction. _Feet and Hands of Man, considered as Difficulties on the Theory ofNatural Selection. _ There are a few other physical characteristics of man, that may just bementioned as offering similar difficulties, though I do not attach thesame importance to them as to those I have already dwelt on. Thespecialization and perfection of the hands and feet of man seemsdifficult to account for. Throughout the whole of the quadrumana thefoot is prehensile; and a very rigid selection must therefore have beenneeded to bring about that arrangement of the bones and muscles, whichhas converted the thumb into a great toe, so completely, that the powerof opposability is totally lost in every race, whatever some travellersmay vaguely assert to the contrary. It is difficult to see why theprehensile power should have been taken away. It must certainly havebeen useful in climbing, and the case of the baboons shows that it isquite compatible with terrestrial locomotion. It may not be compatiblewith perfectly easy erect locomotion; but, then, how can we conceivethat early man, _as an animal_, gained anything by purely erectlocomotion? Again, the hand of man contains latent capacities and powerswhich are unused by savages, and must have been even less used bypalæolithic man and his still ruder predecessors. It has all theappearance of an organ prepared for the use of civilized man, and onewhich was required to render civilization possible. Apes make little useof their separate fingers and opposable thumbs. They grasp objectsrudely and clumsily, and look as if a much less specialized extremitywould have served their purpose as well. I do not lay much stress onthis, but, if it be proved that some intelligent power has guided ordetermined the development of man, then we may see indications of thatpower, in facts which, by themselves, would not serve to prove itsexistence. _The voice of man. _--The same remark will apply to another peculiarlyhuman character, the wonderful power, range, flexibility, and sweetness, of the musical sounds producible by the human larynx, especially in thefemale sex. The habits of savages give no indication of how this facultycould have been developed by natural selection; because it is neverrequired or used by them. The singing of savages is a more or lessmonotonous howling, and the females seldom sing at all. Savagescertainly never choose their wives for fine voices, but for rude health, and strength, and physical beauty. Sexual selection could not thereforehave developed this wonderful power, which only comes into play amongcivilized people. It seems as if the organ had been prepared inanticipation of the future progress of man, since it contains latentcapacities which are useless to him in his earlier condition. Thedelicate correlations of structure that give it such marvellous powers, could not therefore have been acquired by means of natural selection. _The Origin of some of Man's Mental Faculties, by the preservation ofUseful Variations, not possible. _ Turning to the mind of man, we meet with many difficulties in attemptingto understand, how those mental faculties, which are especially human, could have been acquired by the preservation of useful variations. Atfirst sight, it would seem that such feelings as those of abstractjustice and benevolence could never have been so acquired, because theyare incompatible with the law of the strongest, which is the essence ofnatural selection. But this is, I think, an erroneous view, because wemust look, not to individuals but to societies; and justice andbenevolence, exercised towards members of the same tribe, wouldcertainly tend to strengthen that tribe, and give it a superiority overanother in which the right of the strongest prevailed, and whereconsequently the weak and the sickly were left to perish, and the fewstrong ruthlessly destroyed the many who were weaker. But there is another class of human faculties that do not regard ourfellow men, and which cannot, therefore, be thus accounted for. Such arethe capacity to form ideal conceptions of space and time, of eternityand infinity--the capacity for intense artistic feelings of pleasure, inform, colour, and composition--and for those abstract notions of formand number which render geometry and arithmetic possible. How were allor any of these faculties first developed, when they could have been ofno possible use to man in his early stages of barbarism? How could"natural selection, " or survival of the fittest in the struggle forexistence, at all favour the development of mental powers so entirelyremoved from the material necessities of savage men, and which even now, with our comparatively high civilization, are, in their farthestdevelopments, in advance of the age, and appear to have relation ratherto the future of the race than to its actual status? _Difficulty as to the Origin of the Moral Sense. _ Exactly the same difficulty arises, when we endeavour to account for thedevelopment of the moral sense or conscience in savage man; for althoughthe _practice_ of benevolence, honesty, or truth, may have been usefulto the tribe possessing these virtues, that does not at all account forthe peculiar _sanctity_, attached to actions which each tribe considersright and moral, as contrasted with the very different feelings withwhich they regard what is merely _useful_. The utilitarian hypothesis(which is the theory of natural selection applied to the mind) seemsinadequate to account for the development of the moral sense. Thissubject has been recently much discussed, and I will here only give oneexample to illustrate my argument. The utilitarian sanction fortruthfulness is by no means very powerful or universal. Few laws enforceit. No very severe reprobation follows untruthfulness. In all ages andcountries, falsehood has been thought allowable in love, and laudable inwar; while, at the present day, it is held to be venial by the majorityof mankind, in trade, commerce, and speculation. A certain amount ofuntruthfulness is a necessary part of politeness in the east and westalike, while even severe moralists have held a lie justifiable, to eludean enemy or prevent a crime. Such being the difficulties with which thisvirtue has had to struggle, with so many exceptions to its practice, with so many instances in which it brought ruin or death to its tooardent devotee, how can we believe that considerations of utility couldever invest it with the mysterious sanctity of the highestvirtue, --could ever induce men to value truth for its own sake, andpractice it regardless of consequences? Yet, it is a fact, that such a mystical sense of wrong does attach tountruthfulness, not only among the higher classes of civilized people, but among whole tribes of utter savages. Sir Walter Elliott tells us (inhis paper "On the Characteristics of the Population of Central andSouthern India, " published in the Journal of the Ethnological Society ofLondon, vol. I. , p. 107) that the Kurubars and Santals, barbaroushill-tribes of Central India, are noted for veracity. It is a commonsaying that "a Kurubar _always_ speaks the truth;" and Major Jervissays, "the Santals are the most truthful men I ever met with. " As aremarkable instance of this quality the following fact is given. Anumber of prisoners, taken during the Santal insurrection, were allowedto go free on parole, to work at a certain spot for wages. After sometime cholera attacked them and they were obliged to leave, but every manof them returned and gave up his earnings to the guard. Two hundredsavages with money in their girdles, walked thirty miles back to prisonrather than break their word! My own experience among savages hasfurnished me with similar, although less severely tested, instances; andwe cannot avoid asking, how is it, that in these few cases "experiencesof utility" have left such an overwhelming impression, while in so manyothers they have left none? The experiences of savage men as regards theutility of truth, must, in the long run, be pretty nearly equal. How isit, then, that in some cases the result is a sanctity which overridesall considerations of personal advantage, while in others there ishardly a rudiment of such a feeling? The intuitional theory, which I am now advocating, explains this by thesupposition, that there is a feeling--a sense of right and wrong--in ournature, antecedent to and independent of experiences of utility. Wherefree play is allowed to the relations between man and man, this feelingattaches itself to those acts of universal utility or self-sacrifice, which are the products of our affections and sympathies, and which weterm moral; while it may be, and often is, perverted, to give the samesanction to acts of narrow and conventional utility which are reallyimmoral, --as when the Hindoo will tell a lie, but will sooner starvethan eat unclean food; and looks upon the marriage of adult females asgross immorality. The strength of the moral feeling will depend upon individual or racialconstitution, and on education and habit;--the acts to which itssanctions are applied, will depend upon how far the simple feelings andaffections of our nature, have been modified by custom, by law, or byreligion. It is difficult to conceive that such an intense and mystical feeling ofright and wrong, (so intense as to overcome all ideas of personaladvantage or utility), could have been developed out of accumulatedancestral experiences of utility; and still more difficult tounderstand, how feelings developed by one set of utilities, could betransferred to acts of which the utility was partial, imaginary, oraltogether absent. But if a moral sense is an essential part of ournature, it is easy to see, that its sanction may often be given to actswhich are useless or immoral; just as the natural appetite for drink, isperverted by the drunkard into the means of his destruction. _Summary of the Argument as to the Insufficiency of Natural Selection toaccount for the Development of Man. _ Briefly to resume my argument--I have shown that the brain of the lowestsavages, and, as far as we yet know, of the pre-historic races, islittle inferior in size to that of the highest types of man, andimmensely superior to that of the higher animals; while it isuniversally admitted that quantity of brain is one of the mostimportant, and probably the most essential, of the elements whichdetermine mental power. Yet the mental requirements of savages, and thefaculties actually exercised by them, are very little above those ofanimals. The higher feelings of pure morality and refined emotion, andthe power of abstract reasoning and ideal conception, are useless tothem, are rarely if ever manifested, and have no important relations totheir habits, wants, desires, or well-being. They possess a mental organbeyond their needs. Natural Selection could only have endowed savage manwith a brain a little superior to that of an ape, whereas he actuallypossesses one very little inferior to that of a philosopher. The soft, naked, sensitive skin of man, entirely free from that hairycovering which is so universal among other mammalia, cannot be explainedon the theory of natural selection. The habits of savages show that theyfeel the want of this covering, which is most completely absent in manexactly where it is thickest in other animals. We have no reasonwhatever to believe, that it could have been hurtful, or even useless toprimitive man; and, under these circumstances, its complete abolition, shown by its never reverting in mixed breeds, is a demonstration of theagency of some other power than the law of the survival of the fittest, in the development of man from the lower animals. Other characters show difficulties of a similar kind, though not perhapsin an equal degree. The structure of the human foot and hand seemunnecessarily perfect for the needs of savage man, in whom they are ascompletely and as humanly developed as in the highest races. Thestructure of the human larynx, giving the power of speech and ofproducing musical sounds, and especially its extreme development in thefemale sex, are shown to be beyond the needs of savages, and from theirknown habits, impossible to have been acquired either by sexualselection, or by survival of the fittest. The mind of man offers arguments in the same direction, hardly lessstrong than those derived from his bodily structure. A number of hismental faculties have no relation to his fellow men, or to his materialprogress. The power of conceiving eternity and infinity, and all thosepurely abstract notions of form, number, and harmony, which play solarge a part in the life of civilised races, are entirely outside of theworld of thought of the savage, and have no influence on his individualexistence or on that of his tribe. They could not, therefore, have beendeveloped by any preservation of useful forms of thought; yet we findoccasional traces of them amidst a low civilization, and at a time whenthey could have had no practical effect on the success of theindividual, the family, or the race; and the development of a moralsense or conscience by similar means is equally inconceivable. But, on the other hand, we find that every one of these characteristicsis necessary for the full development of human nature. The rapidprogress of civilization under favourable conditions, would not bepossible, were not the organ of the mind of man prepared in advance, fully developed as regards size, structure, and proportions, and onlyneeding a few generations of use and habit to co-ordinate its complexfunctions. The naked and sensitive skin, by necessitating clothing andhouses, would lead to the more rapid development of man's inventive andconstructive faculties; and, by leading to a more refined feeling ofpersonal modesty, may have influenced, to a considerable extent, hismoral nature. The erect form of man, by freeing the hands from alllocomotive uses, has been necessary for his intellectual advancement;and the extreme perfection of his hands, has alone rendered possiblethat excellence in all the arts of civilization which raises him so farabove the savage, and is perhaps but the forerunner of a higherintellectual and moral advancement. The perfection of his vocal organshas first led to the formation of articulate speech, and then to thedevelopment of those exquisitely toned sounds, which are onlyappreciated by the higher races, and which are probably destined formore elevated uses and more refined enjoyment, in a higher conditionthan we have yet attained to. So, those faculties which enable us totranscend time and space, and to realize the wonderful conceptions ofmathematics and philosophy, or which give us an intense yearning forabstract truth, (all of which were occasionally manifested at such anearly period of human history as to be far in advance of any of the fewpractical applications which have since grown out of them), areevidently essential to the perfect development of man as a spiritualbeing, but are utterly inconceivable as having been produced through theaction of a law which looks only, and can look only, to the immediatematerial welfare of the individual or the race. The inference I would draw from this class of phenomena is, that asuperior intelligence has guided the development of man in a definitedirection, and for a special purpose, just as man guides the developmentof many animal and vegetable forms. The laws of evolution alone would, perhaps, never have produced a grain so well adapted to man's use aswheat and maize; such fruits as the seedless banana and bread-fruit; orsuch animals as the Guernsey milch cow, or the London dray-horse. Yetthese so closely resemble the unaided productions of nature, that we maywell imagine a being who had mastered the laws of development of organicforms through past ages, refusing to believe that any new power had beenconcerned in their production, and scornfully rejecting the theory (asmy theory will be rejected by many who agree with me on other points), that in these few cases a controlling intelligence had directed theaction of the laws of variation, multiplication, and survival, for hisown purposes. We know, however, that this has been done; and we musttherefore admit the possibility that, if we are not the highestintelligences in the universe, some higher intelligence may havedirected the process by which the human race was developed, by means ofmore subtle agencies than we are acquainted with. At the same time Imust confess, that this theory has the disadvantage of requiring theintervention of some distinct individual intelligence, to aid in theproduction of what we can hardly avoid considering as the ultimate aimand outcome of all organized existence--intellectual, ever-advancing, spiritual man. It therefore implies, that the great laws which governthe material universe were insufficient for his production, unless weconsider (as we may fairly do) that the controlling action of suchhigher intelligences is a necessary part of those laws, just as theaction of all surrounding organisms is one of the agencies in organicdevelopment. But even if my particular view should not be the true one, the difficulties I have put forward remain, and I think prove, that somemore general and more fundamental law underlies that of "naturalselection. " The law of "unconscious intelligence" pervading all organicnature, put forth by Dr. Laycock and adopted by Mr. Murphy, is such alaw; but to my mind it has the double disadvantage of being bothunintelligible and incapable of any kind of proof. It is more probable, that the true law lies too deep for us to discover it; but there seemsto me, to be ample indications that such a law does exist, and isprobably connected with the absolute origin of life and organization. (_Note A. _) _The Origin of Consciousness. _ The question of the origin of sensation and of thought can be butbriefly discussed in this place, since it is a subject wide enough torequire a separate volume for its proper treatment. No physiologist orphilosopher has yet ventured to propound an intelligible theory, of howsensation may possibly be a product of organization; while many havedeclared the passage from matter to mind to be inconceivable. In hispresidential address to the Physical Section of the British Associationat Norwich, in 1868, Professor Tyndall expressed himself as follows:-- "The passage from the physics of the brain to the corresponding facts ofconsciousness is unthinkable. Granted that a definite thought, and adefinite molecular action in the brain occur simultaneously, we do notpossess the intellectual organ, nor apparently any rudiment of theorgan, which would enable us to pass by a process of reasoning from theone phenomenon to the other. They appear together, but we do not knowwhy. Were our minds and senses so expanded, strengthened, andilluminated as to enable us to see and feel the very molecules of thebrain; were we capable of following all their motions, all theirgroupings, all their electric discharges, if such there be, and were weintimately acquainted with the corresponding states of thought andfeeling, we should be as far as ever from the solution of the problem, 'How are these physical processes connected with the facts ofconsciousness?' The chasm between the two classes of phenomena wouldstill remain intellectually impassable. " In his latest work ("An Introduction to the Classification of Animals, ")published in 1869, Professor Huxley unhesitatingly adopts the "wellfounded doctrine, that life is the cause and not the consequence oforganization. " In his celebrated article "On the Physical Basis ofLife, " however, he maintains, that life is a property of protoplasm, andthat protoplasm owes its properties to the nature and disposition of itsmolecules. Hence he terms it "the matter of life, " and believes that allthe physical properties of organized beings are due to the physicalproperties of protoplasm. So far we might, perhaps, follow him, but hedoes not stop here. He proceeds to bridge over that chasm whichProfessor Tyndall has declared to be "intellectually impassable, " and, by means which he states to be logical, arrives at the conclusion, thatour "_thoughts are the expression of molecular changes in that matter oflife which is the source of our other vital phenomena_. " Not having beenable to find any clue in Professor Huxley's writings, to the steps bywhich he passes from those vital phenomena, which consist only, in theirlast analysis, of movements of particles of matter, to those otherphenomena which we term thought, sensation, or consciousness; but, knowing that so positive an expression of opinion from him will havegreat weight with many persons, I shall endeavour to show, with as muchbrevity as is compatible with clearness, that this theory is not onlyincapable of proof, but is also, as it appears to me, inconsistent withaccurate conceptions of molecular physics. To do this, and in orderfurther to develop my views, I shall have to give a brief sketch of themost recent speculations and discoveries, as to the ultimate nature andconstitution of matter. _The Nature of Matter. _ It has been long seen by the best thinkers on the subject, thatatoms, --considered as minute solid bodies from which emanate theattractive and repulsive forces which give what we term matter itsproperties, --could serve no purpose whatever; since it is universallyadmitted that the supposed atoms never touch each other, and it cannotbe conceived that these homogeneous, indivisible, solid units, arethemselves the ultimate _cause_ of the forces that emanate from theircentres. As, therefore, none of the properties of matter can be due tothe atoms themselves, but only to the forces which emanate from thepoints in space indicated by the atomic centres, it is logicalcontinually to diminish their size till they vanish, leaving onlylocalized centres of force to represent them. Of the various attemptsthat have been made to show how the properties of matter may be due tosuch modified atoms (considered as mere centres of force), the mostsuccessful, because the simplest and the most logical, is that of Mr. Bayma, who, in his "Molecular Mechanics, " has demonstrated how, from thesimple assumption of such centres having attractive and repulsive forces(both varying according to the same law of the inverse squares asgravitation), and by grouping them in symmetrical figures, consisting ofa repulsive centre, an attractive nucleus, and one or more repulsiveenvelopes, we may explain all the general properties of matter; and, bymore and more complex arrangements, even the special chemical, electrical, and magnetic properties of special forms of matter. [I] Eachchemical element will thus consist of a molecule formed of simple atoms, (or as Mr. Bayma terms them to avoid confusion, "material elements") ingreater or less number and of more or less complex arrangement; whichmolecule is in stable equilibrium, but liable to be changed in form bythe attractive or repulsive influences of differently constitutedmolecules, constituting the phenomena of chemical combination, andresulting in new forms of molecule of greater complexity and more orless stability. +--------------------------------------------------------------+ | [I] Mr. Bayma's work, entitled "The Elements of Molecular | | Mechanics, " was published in 1866, and has received less | | attention than it deserves. It is characterised by great | | lucidity, by logical arrangement, and by comparatively | | simple geometrical and algebraical demonstrations, so that | | it may be understood and appreciated with a very moderate | | knowledge of mathematics. It consists of a series of | | Propositions, deduced from the known properties of matter; | | from these are derived a number of Theorems, by whose help | | the more complicated Problems are solved. Nothing is taken | | for granted throughout the work, and the only valid mode of | | escaping from its conclusions is, by either disproving the | | fundamental Propositions, or by detecting fallacies in the | | subsequent reasoning. | +--------------------------------------------------------------+ Those organic compounds of which organized beings are built up, consist, as is well known, of matter of an extreme complexity. And greatinstability; whence result the changes of form to which it iscontinually subject. This view enables us to comprehend the_possibility_, of the phenomena of vegetative life being due to analmost infinite complexity of molecular combinations, subject todefinite changes under the stimuli of heat, moisture, light, electricity, and probably some unknown forces. But this greater andgreater complexity, even if carried to an infinite extent, cannot, ofitself, have the slightest tendency to originate consciousness in suchmolecules or groups of molecules. If a material element, or acombination of a thousand material elements in a molecule, are alikeunconscious, it is impossible for us to believe, that the mere additionof one, two, or a thousand other material elements to form a morecomplex molecule, could in any way tend to produce a self-consciousexistence. The things are radically distinct. To say that mind is aproduct or function of protoplasm, or of its molecular changes, is touse words to which we can attach no clear conception. You cannot have, in the whole, what does not exist in any of the parts; and those whoargue thus should put forth a definite conception of matter, withclearly enunciated properties, and show, that the necessary result of acertain complex arrangement of the elements or atoms of that matter, will be the production of self-consciousness. There is no escape fromthis dilemma, --either all matter is conscious, or consciousness issomething distinct from matter, and in the latter case, its presence inmaterial forms is a proof of the existence of conscious beings, outsideof, and independent of, what we term matter. (_Note B. _) _Matter is Force. _--The foregoing considerations lead us to the veryimportant conclusion, that matter is essentially force, and nothing butforce; that matter, as popularly understood, does not exist, and is, infact, philosophically inconceivable. When we touch matter, we onlyreally experience sensations of resistance, implying repulsive force;and no other sense can give us such apparently solid proofs of thereality of matter, as touch does. This conclusion, if kept constantlypresent in the mind, will be found to have a most important bearing onalmost every high scientific and philosophical problem, and especiallyon such as relate to our own conscious existence. _All Force is probably Will-Force. _--If we are satisfied that force orforces are all that exist in the material universe, we are next led toenquire what is force? We are acquainted with two radically distinct orapparently distinct kinds of force--the first consists of the primaryforces of nature, such as gravitation, cohesion, repulsion, heat, electricity, &c. ; the second is our own will-force. Many persons will atonce deny that the latter exists. It will be said, that it is a meretransformation of the primary forces before alluded to; that thecorrelation of forces includes those of animal life, and that _will_itself is but the result of molecular change in the brain. I think, however, that it can be shown, that this latter assertion has neitherbeen proved, nor even been proved to be possible; and that in making it, a great leap in the dark has been taken from the known to the unknown. It may be at once admitted that the _muscular force_ of animals and men, is merely the transformed energy derived from the primary forces ofnature. So much has been, if not rigidly proved, yet rendered highlyprobable, and it is in perfect accordance with all our knowledge ofnatural forces and natural laws. But it cannot be contended that thephysiological balance-sheet has ever been so accurately struck, that weare entitled to say, not one-thousandth part of a grain more of forcehas been exerted by any organized body or in any part of it, than hasbeen derived from the known primary forces of the material world. Ifthat were so, it would absolutely negative the existence of will; for ifwill is anything, it is a power that _directs_ the action of the forcesstored up in the body, and it is not conceivable that this _direction_can take place, without the exercise of some force in some part of theorganism. However delicately a machine may be constructed, with the mostexquisitely contrived detents to release a weight or spring by theexertion of the smallest possible amount of force, _some_ external forcewill always, be required; so, in the animal machine, however minute maybe the changes required in the cells or fibres of the brain, to set inmotion the nerve currents which loosen or excite the pent up forces ofcertain muscles, _some force_ must be required to effect those changes. If it is said, "those changes are automatic, and are set in motion byexternal causes, " then one essential part of our consciousness, acertain amount of freedom in willing, is annihilated; and it isinconceivable how or why there should have arisen any consciousness orany apparent will, in such purely automatic organisms. If this were so, our apparent WILL would be a delusion, and Professor Huxley'sbelief--"that our volition counts for something as a condition of thecourse of events, " would be fallacious, since our volition would then bebut one link in the chain of events, counting for neither more nor lessthan any other link whatever. If, therefore, we have traced one force, however minute, to an origin inour own WILL, while we have no knowledge of any other primary cause offorce, it does not seem an improbable conclusion that all force may bewill-force; and thus, that the whole universe, is not merely dependenton, but actually _is_, the WILL of higher intelligences or of oneSupreme Intelligence. It has been often said that the true poet is aseer; and in the noble verse of an American poetess, we find expressed, what may prove to be the highest fact of science, the noblest truth ofphilosophy: God of the Granite and the Rose! Soul of the Sparrow and the Bee! The mighty tide of Being flows Through countless channels, Lord, from thee. It leaps to life in grass and flowers, Through every grade of being runs, While from Creation's radiant towers Its glory flames in Stars and Suns. _Conclusion. _ These speculations are usually held to be far beyond the bounds ofscience; but they appear to me to be more legitimate deductions from thefacts of science, than those which consist in reducing the wholeuniverse, not merely to matter, but to matter conceived and defined soas to be philosophically inconceivable. It is surely a great step inadvance, to get rid of the notion that _matter_ is a thing of itself, which can exist _per se_, and must have been eternal, since it issupposed to be indestructible and uncreated, --that force, or the forcesof nature, are another thing, given or added to matter, or else itsnecessary properties, --and that mind is yet another thing, either aproduct of this matter and its supposed inherent forces, or distinctfrom and co-existent with it;--and to be able to substitute for thiscomplicated theory, which leads to endless dilemmas and contradictions, the far simpler and more consistent belief, that matter, as an entitydistinct from force, does not exist; and that FORCE is a product ofMIND. Philosophy had long demonstrated our incapacity to prove theexistence of matter, as usually conceived; while it admitted thedemonstration to each of us of our own self-conscious, ideal existence. Science has now worked its way up to the same result, and this agreementbetween them should give us some confidence in their combined teaching. The view we have now arrived at seems to me more grand and sublime, aswell as far simpler, than any other. It exhibits the universe, as auniverse of intelligence and will-power; and by enabling us to ridourselves of the impossibility of thinking of mind, but as connectedwith our old notions of matter, opens up infinite possibilities ofexistence, connected with infinitely varied manifestations of force, totally distinct from, yet as real as, what we term matter. The grand law of continuity which we see pervading our universe, wouldlead us to infer infinite gradations of existence, and to people allspace with intelligence and will-power; and, if so, we have nodifficulty in believing that for so noble a purpose as the progressivedevelopment of higher and higher intelligences, those primal and generalwill-forces, which have sufficed for the production of the loweranimals, should have been guided into new channels and made to convergein definite directions. And if, as seems to me probable, this has beendone, I cannot admit that it in any degree affects the truth orgenerality of Mr. Darwin's great discovery. It merely shows, that thelaws of organic development have been occasionally used for a specialend, just as man uses them for his special ends; and, I do not see thatthe law of "natural selection" can be said to be disproved, if it can beshown that man does not owe his entire physical and mental developmentto its unaided action, any more than it is disproved by the existence ofthe poodle or the pouter pigeon, the production of which may have beenequally beyond its undirected power. The objections which in this essay I have taken, to the view, --that thesame law which appears to have sufficed for the development of animals, has been alone the cause of man's superior physical and mentalnature, --will, I have no doubt, be over-ruled and explained away. But Iventure to think they will nevertheless maintain their ground, and thatthey can only be met by the discovery of new facts or new laws, of anature very different from any yet known to us. I can only hope that mytreatment of the subject, though necessarily very meagre, has been clearand intelligible; and that it may prove suggestive, both to theopponents and to the upholders of the theory of Natural Selection. NOTES. _NOTE A. _ (_Page_ 360. ) Some of my critics seem quite to have misunderstood my meaning in thispart of the argument. They have accused me of unnecessarily andunphilosophically appealing to "first causes" in order to get over adifficulty--of believing that "our brains are made by God and our lungsby natural selection;" and that, in point of fact, "man is God'sdomestic animal. " An eminent French critic, M. Claparède, makes mecontinually call in the aid of--"_une Force supérieure_, " the capital F, meaning I imagine that this "higher Force" is the Deity. I can onlyexplain this misconception by the incapacity of the modern cultivatedmind to realise the existence of any higher intelligence between itselfand Deity. Angels and archangels, spirits and demons, have been so longbanished from our belief as to have become actually unthinkable asactual existences, and nothing in modern philosophy takes their place. Yet the grand law of "continuity, " the last outcome of modern science, which seems absolute throughout the realms of matter, force, and mind, so far as we can explore them, cannot surely fail to be true beyond thenarrow sphere of our vision, and leave an infinite chasm between man andthe Great Mind of the universe. Such a supposition seems to me in thehighest degree improbable. Now, in referring to the origin of man, and its possible determiningcauses, I have used the words "some other power"--"some intelligentpower"--"a superior intelligence"--"a controlling intelligence, " andonly in reference to the origin of universal forces and laws have Ispoken of the will or power of "one Supreme Intelligence. " These are theonly expressions I have used in alluding to the power which I believehas acted in the case of man, and they were purposely chosen to show, that I reject the hypothesis of "first causes" for any and every_special_ effect in the universe, except in the same sense that theaction of man or of any other intelligent being is a first cause. Inusing such terms I wished to show plainly, that I contemplated thepossibility that the development of the essentially human portions ofman's structure and intellect may have been determined by the directinginfluence of some higher intelligent beings, acting through natural anduniversal laws. A belief of this nature may or may not have afoundation, but it is an intelligible theory, and is not, _in itsnature_, incapable of proof; and it rests on facts and arguments of anexactly similar kind to those, which would enable a sufficientlypowerful intellect to deduce, from the existence on the earth ofcultivated plants and domestic animals, the presence of some intelligentbeing of a higher nature than themselves. _NOTE B. _ (_Page_ 365. ) A friend has suggested that I have not here explained myselfsufficiently, and objects, that _life_ does not exist in matter any morethan _consciousness_, and if the one can be produced by the laws ofmatter, why may not the other? I reply, that there is a radicaldifference between the two. Organic or vegetative life consistsessentially in chemical transformations and molecular motions, occurringunder certain conditions and in a certain order. The matter, and theforces which act upon it, are for the most part known; and if there areany forces engaged in the manifestation of vegetative life yetundiscovered (which is a moot question), we can conceive them asanalogous to such forces as heat, electricity, or chemical affinity, with which we are already acquainted. We can thus clearly _conceive_ ofthe transition from dead matter to living matter. A complex mass whichsuffers decomposition or decay is dead, but if this mass has the powerof attracting to itself, from the surrounding medium, matter like thatof which it is composed, we have the first rudiment of vegetative life. If the mass can do this for a considerable time, and if its absorptionof new matter more than replaces that lost by decomposition, and if itis of such a nature as to resist the mechanical or chemical forces towhich it is usually exposed, and to retain a tolerably constant form, weterm it a living organism. We can _conceive_ an organism to be soconstituted, and we can further conceive that any fragments, which maybe accidentally broken from it, or which may fall away when its bulk hasbecome too great for the cohesion of all its parts, may begin toincrease anew and run the same course as the parent mass. This is growthand reproduction in their simplest forms; and from such a simplebeginning it is possible to conceive a series of slight modifications ofcomposition, and of internal and external forces, which shouldultimately lead to the development of more complex organisms. The LIFEof such an organism may, perhaps, be nothing added to it, but merely thename we give to the result of a balance of internal and external forcesin maintaining the permanence of the form and structure of theindividual. The simplest conceivable form of such life would be thedewdrop, which owes its existence to the balance between thecondensation of aqueous vapour in the atmosphere and the evaporation ofits substance. If either is in excess, it soon ceases to maintain anindividual existence. I do not maintain that vegetative life _is_ whollydue to such a complex balance of forces, but only that it is_conceivable_ as such. With CONSCIOUSNESS the case is very different. Its phenomena are notcomparable with those of any kind of _matter_ subjected to any of theknown or conceivable _forces_ of nature; and we cannot _conceive_ agradual transition from absolute unconsciousness to consciousness, froman unsentient organism to a sentient being. The merest rudiment ofsensation or self-consciousness is infinitely removed from absolutelynon-sentient or unconscious matter. We can conceive of no physicaladdition to, or modification of, an unconscious mass which should createconsciousness; no step in the series of changes organised matter mayundergo, which should bring in sensation where there was no sensationor power of sensation at the preceding step. It is because the thingsare utterly incomparable and incommensurable that we can only conceiveof _sensation_ coming to matter from without, while _life_ may beconceived as merely a specific combination and co-ordination of thematter and the forces that compose the universe, and with which we areseparately acquainted. We may admit with Professor Huxley that_protoplasm_ is the "matter of life" and the cause of organisation, butwe cannot admit or conceive that _protoplasm_ is the primary source ofsensation and consciousness, or that it can ever of itself become_conscious_ in the same way as we may perhaps conceive that it maybecome _alive_. INDEX. _ABRAXAS grossulariata_, 119. _Acanthotritus dorsalis_, 94. _Accipiter pileatus_, 107. ACRÆIDÆ, the subjects of mimicry, 85, 86. _Acronycta psi_, protective colouring of, 62. ADAPTATION brought about by general laws, 276; looks like design, 281. ÆGERIIDÆ mimic Hymenoptera, 90. AGASSIZ, or embryonic character of ancient animals, 301. _Agnia fasciata_, mimics another Longicorn, 95. _Agriopis aprilina_, protective colouring of, 62. ALCEDINIDÆ, sexual colouring and nidification of, 240. AMADINA, sexual colouring and nidification of, 243. AMPELIDÆ, sexual colouring and nidification of, 243. ANCYLOTHERIUM, 300. ANDRENIDÆ, 98. _Angræcum sesquipedale_, 272; its fertilization by a large moth, 275. ANIMALS, senses and faculties of, 127; intellect of, compared with that of savages, 341. ANISOCERINÆ, 92. ANOA, 196. ANOPLOTHERIUM, 299. ANTHRIBIDÆ, mimicry of, 94; dimorphism in, 155. _Anthrocera filipendulæ_, 120. ANTHROPOLOGISTS, wide difference of opinion among, as to origin of human races, 304; conflicting views of, harmonized, 321. ANTIQUITY of man, 303, 322. APATHUS, 98. APPARENT exceptions to law of colour and nidification, 253. AQUATIC BIRDS, why abundant, 32. _Araschnia prorsa_, 154. ARCHEGOSAURUS, 300. ARCHÆOPTERYX, 300. ARCHITECTURE of most nations derivative, 228; Grecian, false in principle, 226. ARCTIC animals, white colour of, 50, 51. ARGYLL, Duke of, on colours of Woodcock, 53; on mind in nature, 265; criticism on Darwin's works, 269; on humming birds 282; on creation by birth, 287. ASILUS, 97. ASPECTS of nature as influencing man's development, 317. BABIRUSA, 196. BALANCE in nature, 42. BARRINGTON, Hon. Daines, on song of birds, 220. BASILORNIS, 196. BATES, Mr. , first adopted the word "mimicry, " 75; his observations on Leptalis and Heliconidæ, 82; his paper explaining the theory of mimicry, 83; objections to his theory, 108; on variation, 165; on recent immigration of Amazonian Indians, 214. BAYMA, Mr. , on "Molecular Mechanics, " 363, 364. BEAUTY in nature, 282; not universal, 284; of flowers useful to them, 285; not given for its own sake, 285. BIRDS, possible rapid increase of, 29; numbers that die annually, 30; mimicry among, 103; dull colour of females, 114; nidification as affecting colour of females, 116; refusing the gooseberry caterpillar, 119; the highest in rank and organization, 137; dimorphism in, 155; why peculiar nest built by each species, 215-219; build more perfect nests as they grow older, 224, 227; alter and improve their nests, 226; sexual differences of colour in, 239. _Bombus hortorum_, 90. _Bombycilla, garrula_, colours and nidification of, 255. BOMBYLIUS, 98. BRAIN of the savage but slightly less than that of civilized man, 336; size of, an important element of mental power, 335; of savage races larger than their needs require, 338, 343; of man and of anthropoid apes compared, 338. BROCA, Professor Paul, on the fine crania of the cave men, 337. _Bryophila glandifera_ and _B. Perla_ protectively coloured, 63. BUCEROTIDÆ, sexual colouring and nidification of, 241. BUCCONIDÆ, sexual colouring and nidification of, 241. BUFF-TIP moth, resembles a broken stick, 62. BUILDINGS of various races do not change, 213. BUPRESTIDÆ, resembling bird's dung, 57; similar colours in two sexes, 114. BUTTERFLIES, value of, in studying "natural selection, " 131; varieties of, in Sardinia and Isle of Man, 178. _CACIA anthriboides_, 94. _Callizona acesta_, protective colouring of, 59. CALORNIS, 239. CAPITONIDÆ, sexual colouring and nidification of, 241. _Capnolymma stygium_, 94. CARABIDÆ, special protection among, 72; similar colouring of two sexes, 114. CASSIDÆ, resemble dew drops, 58. CATERPILLARS, mimicking a poisonous snake, 99; gaudy colours of, 117; various modes of protection of, 118; gooseberry caterpillar, 119; Mr. Jenner Weir's observations on, 119; Mr. A. G. Butler's observations on, 121. CELEBES, local modifications of form in, 170; probable cause of these, 176; remarkable zoological peculiarities of, 195-199. CENTROPUS, sexual colouring and nidification of, 242. _Cephalodonta spinipes_, 92. _Ceroxylus laceratus_, imitates a moss-covered stick, 64. CERTHIOLA, sexual colouring and nidification of, 244. _Cethosia æole_, 172; _biblis_, 172. CETONIADÆ, how protected, 73; similar colours of two sexes, 114. CEYCOPSIS, 196. _Charis melipona_, 96. CHEMATOBIA, wintry colours of this genus, 62. _Chlamys pilula_, resembles dung of caterpillars, 58. CHRYSIDIDÆ, how protected, 72. CHRYSOMELIDÆ, similar colouring of two sexes, 114. CICINDELA, adaptive colour of various species of, 57. _Cilix compressa_, resembles bird's dung, 63. CLADOBATES, mimicking squirrels, 107. CLASSIFICATION, form of true, 6; circular, inadmissible, 8; quinarian and circular, of Swainson, 46; argument from, against Mr. Darwin, 295. CLIMACTERIS, sexual colouring and nidification of, 243. COCCINELLIDÆ, how protected, 72; similar colouring of sexes, 114. COEXISTING varieties, 159. _Collyrodes lacordairei_, 95. COLOUR, in animals, popular theories of, 47; frequent variations of, in domesticated animals, 48; influenced by need of concealment, 49; in deserts, 49, 50; in Arctic regions, 50, 51; nocturnal, 51; tropical, 52; special modifications of, 52; different distribution of, in butterflies and moths, 58; of autumnal and winter moths, 62; white, generally dangerous and therefore eliminated, 66; why it exists so abundantly although often injurious, 69; influenced by need of protection, 113; of female birds, 114; in relation to nidification of birds, 116; gaudy colours of many caterpillars, 117; in nature, general causes of, 126; local variations of, 173; sexual differences of, in birds, 239; in female birds, how connected with their nidification, 240, 246; more variable than structure or habits, and therefore more easily modified, 249; of flowers, as explained by Mr. Darwin, 262; often correlated with disease, 316. COMPSOGNATHUS, 300. _Condylodera tricondyloides_, 97. CONSCIOUSNESS, origin of, 360; Professor Tyndall on, 361; not a product of complex organization, 365. CORRELATION of growth, 310. _Corynomalus sp. _, 92. COTINGIDÆ, sexual colouring and nidification of, 244. CRATOSOMUS, a hard weevil, 94. CRICKETS mimicking sand wasps, 98. CRYPTODONTIA, 299. _Cucullia verbasci_, 120. CURCULIONIDÆ, often protected by hard covering, 71; similar colours of two sexes, 114. _Cuviera squamata_, 258. _Cyclopeplus batesii_, 92. CYNOPITHECUS, 196. _Cynthia arsinoë_, 172. DANAIDÆ, the subjects of mimicry, 85, 86. _Danais erippus_, 88; _chysippus_, 112; _sobrina_, 179; _aglaia_, 179; _tytia_, 180. DARWIN, Mr. , his principle of utility, 47; on cause of colour in flowers, 127, 262; on colours of caterpillars, 118; on sexual colouration, 260; his metaphors liable to misconception, 269; criticism of, in _North British Review_, 291. DESERT animals, colours of, 49, 50. DIADEMA, species of, mimic Danaidæ, 86, 87; female with male colouration, 112. _Diadema misippus_, 112; _D. Anomala_, 113. _Diaphora mendica_, 89. DICNYODONTIA, 299. DICROURUS, 253. _Diloba coeruleocephala_, 120. DIMORPHISM, 145; in beetles, 155; in birds, 155; illustrated, 157. DINOSAURIA, 298. DIPTERA mimicking wasps and bees, 97. _Doliops curculionides_, 94. DOMESTICATED animals, their essential difference from wild ones, 38-41. DOTTERELL, 251. DRUSILLA, mimicked by three genera, 181. _Drusilla bioculata_, 180. DYTISCUS, dimorphism in, 155. EGYPTIAN architecture, introduced, 225. _Elaps fulvius_, _E. Corallinus_, _E. Lemniscatus_, 101; _E. Mipartitus_, _E. Lemniscatus_, _E. Hemiprichii_, 102. ENODES, 196. ENNOMUS, autumnal colours of this genus, 62. _Eos fuscata_, dimorphism of, 155. EQUUS, 299. _Eronia tritæa_, 172; _valeria_, 172. _Eroschema poweri_, 93. ERYCINIDÆ mimic Heliconidæ, 84. _Erythroplatis corallifer_, 92. ESTRELDA, sexual colouring and nidification of, 243. EUCNEMIDÆ, mimicking a Malacoderm, 93. _Eudromias morinellus_, 251. _Euglossa dimidiata_, 98. EUMORPHIDÆ, a protected group 72; imitated by Longicorns, 92. EUPLOEA, local modifications of colour in, 173. _Euploea midamus_, 87-113, 179; _E. Rhadamanthus_, 87, 179. _Eurhinia megalonice_, 172; _polynice_, 172. EURYLÆMIDÆ, sexual colouring and nidification of, 243. EXTINCT animals, intermediate forms of, 298. EXTINCTION of lower races, 318. FEMALE birds, colours of, 114; sometimes connected with their mode of nidification, 240; more exposed to enemies than the males, 248. FEMALE butterflies generally dull-coloured, 259. FEMALE insects, mimicry by, 110, 259; colours of, 113. FEMALE sex, has no incapacity for as brilliant colouration as the male, 247; in some groups requires more protection than the male, 258. FISHES, protective colouring of, 55. FISSIROSTRAL birds, nests of, 238. FLOWERS, causes of colour in, 127. FLYCATCHERS, genera of, absent from Celebes, 177. FORBES, EDWARD, objections to his theory of Polarity, 17-23. FORCE is probably all Will-force, 366. GALAPAGOS, 10. GALTON, Mr. , on range of intellectual power, 339. GANOCEPHALA, 298. _Gastropacha querci_, protective colour and form of, 62. GAUDRY, M. , on fossil mammals of Greece, 299. GEOGRAPHICAL distribution, dependent on geologic changes, 1; its agreement with law of introduction of new species, 9; of allied species and groups, 12. GEOLOGICAL distribution analogous to geographical, 13. GEOLOGY, facts proved by, 2-5. GIRAFFE, how it acquired its long neck, 42. GLÆA, autumnal colours of this genus, 62. GOULD, Mr. , on sexual plumage of Gray Phalarope, 115; on incubation by male Dotterell, 115. _Grallina australis_, 254. GREEN birds almost confined to the tropics, 52. _Gymnocerus cratosomoides_, 94. _Gymnocerous capucinus_, 96. _Gymnocerous dulcissimus_, 97. GUNTHER, Dr. , on arboreal snakes, 55; on colouring of snakes, 102. _Gynecia dirce_, 59. HABITS, often persistent when use of them has ceased, 234; of children and savages analogous to those of animals, 235; if persistent and imitative may be termed hereditary, 235, 236. HAIRY covering of Mammalia, use of, 344; absence of, in man remarkable, 345; the want of it felt by savages, 346; could not have been abolished by natural selection, 348. _Harpagus diodon_, 107. HEILIPLUS, a hard genus of Curculionidæ, 94. HELICONIDÆ, the objects of mimicry, 77; their secretions, 88; not attacked by birds, 79; sometimes mimicked by other Heliconidæ, 85. HELLADOTHERIUM, 300. HEMIPTERA, protected by bad odour, 72. HERBERT, Rev. W. , on song of birds, 221. HESPERIDÆ, probable means of protection of, 176. HESTHESIS, longicorns resembling ants, 96. _Hestia leuconoë_, 180. HEWITSON, Mr. , 131. HIPPARION, 299. HIPPOTHERIUM, 299. HISPIDÆ, imitated by Longicorns, 92. HOLOTHURIDÆ, 258. _Homalocranium semicinctum_, 101. HOOKER, Dr. , on the value of the "specific term, " 165. HOUSES of American and Malay races contrasted, 213. HUXLEY, Professor, on "Physical Basis of Life, " 362; on volition, 368. HYÆNICTIS, 300. HYBERNIA, wintry colours of this genus, 62. HYMENOPTERA, large number of, peculiar to Celebes, 196. ICTERIDÆ, sexual colouring and nidification of, 244. ICTHYOPTERYGIA, 298. _Ideopsis daos_, 180. IMITATION, the effects of, in man's works, 212. INDIANS, how they travel through trackless forests, 207. INSECTS, protective colouring of, 56; mimicking species of other orders, 97; senses of, perhaps different from ours, 202, 203. INSTINCT, how it may be best studied, 201; definition of, 203; in many cases assumed without proof, 205; if possessed by man, 206; supposed, of Indians, 207; supposed to be shown in the construction of birds' nests, 211. INTELLECT of savages compared with that of animals, 341. INTELLECTUAL power, range of, in man, 339. _Iphias glaucippe_, 172. ITHOMIA, mimicked by Leptalis, 83. _Ithomia ilerdina_, mimicked by four groups of Lepidoptera, 84. JAVA, relations of, to Sumatra and Borneo, 193. JAMAICA swift altering position of nest, 228. JERDON, Mr. , on incubation by males in Turnix, 115. _Kallima inachis_ and _Kallima paralekta_, wonderful resemblance of, to leaves, 59-61. LABYRINTHODONTIA, 298, 300. LAKES as cases of imperfect adaptation, 278. LANIADÆ, sexual colouring and nidification of, 245. LAMARCK'S hypothesis very different from the author's, 41. _Larentia tripunctaria_, 63. LAW which has regulated the introduction of new species, 5; confirmed by geographical distribution, 9; high organization of ancient animals consistent with, 14; of multiplication in geometrical progression, 265; of limited populations, 265; of heredity, 266; of variation, 266; of change of physical conditions, 266; of the equilibrium of nature, 266; as opposed to continual interference, 268. LAYCOCK, Dr. , on law of "unconscious intelligence, " 360. LEAF BUTTERFLY, appearance and habits of, 59-61. LEPIDOPTERA, especially subject to variation, 132. LEPTALIS, species of mimic Heliconidæ, 82; gain a protection thereby, 259. LESTER, Mr. J. M. , on wood-dove and robin, 53. LEVAILLANT, on formation of a nest, 224. _Limenitis archippus_, 88. _Limenitis limire_, 172; _procris_, 172. LIZARDS refusing certain moths and caterpillars, 121; devouring bees, 121. LOCAL FORMS, 158. LOCAL variation of form, 169; of colour, 173; general remarks on, 174; in Celebesian butterflies, probable use of, 175. LOCUSTIDÆ, adaptive colouring of, 64. LUMINOUSNESS of some insects a protection, 71. LYCÆNIDÆ, probable means of protection of, 176. MAMMALS, mimicry among, 107. MAN, does he build by reason or imitation, 212; his works mainly imitative, 225; antiquity of, 303, 322; difference of opinion as to his origin, 304; unity or plurality of species, 305; persistence of type of, 306; importance of mental and moral characters, 312; his dignity and supremacy, 324; his influence on nature, 326; his future development, 326; range of intellectual power in, 339; rudiments of all the higher faculties in savage, 341; his feet and hands, difficulties on the theory of natural selection, 349; his voice, 350; his mental faculties, 351; difficulty as to the origin of the moral sense in, 352; development of, probably directed by a superior intelligence, 359. MANTIDÆ, adaptive colouring of, 64; mimicking white ants, 98. MALACODERMS, a protected group, 93. MALURIDÆ, 255. MATTER, the nature of, 363; Mr. Bayma on, 363; is force, 365. MECHANITIS and Methona, mimicked by _Leptalis_, 83. MECOCERUS, dimorphism of, 155. _Mecocerus gazella_, 94. MEGACEPHALON, 196. MEGAPODIDÆ, sexual colouring and nidification of, 246. MEROPOGON, 196. _Midas dives_, 97. MIMETA, mimicking Tropidorhynchus, 104. MIMICRY, meaning of the word, 74; theory of, 76; among Lepidoptera, 77; how it acts as a protection, 80, 81; of other insects by Lepidoptera, 89; among beetles, 91; of other insects by beetles, 95; of insects by species of other orders, 97; among the vertebrata, 99; among snakes, 101; among tree frogs, 103; among birds, 103; among mammals, 107; objections to the theory of, 108; by female insects, 110; among Papilionidæ, 179; never occurs in the male only, 260. MOMOTIDÆ, sexual colouring and nidification of, 241. MONTROUZIER, M. , on butterflies of Woodlark Island, 152. MORAL sense, difficulty as to the origin of, 352. MORPHOS, how protected, 73. MURRAY, Mr. Andrew, objections to theory of mimicry, 108. MUSCICAPIDÆ, sexual colouring and nidification of, 245. MUSOPHAGIDÆ, sexual colouring and nidification of, 242. NAPEOGENES, all the species are mimickers, 85. NATURAL selection, the principle stated, 41-43; general acceptance of the theory of, 46; tabular demonstration of, 302; outline of theory of, 307; its effects on man and animals different, 311; hardly acts among civilized societies, 330; what it can not do, 333; cannot produce injurious or useless modifications, 334. NECTARINEIDÆ, 254. NECYDALIDÆ, mimic Hymenoptera, 96. _Nemophas grayi_, a Longicorn mimicked by a Longicorn, 95. NESTS of Birds, why different, 215; of young birds, how built, 219; construction of, described by Levaillant, 224; imperfections in, 229; influenced by changed conditions and persistent habits, 232; classification of, according to function, 237. NEW FORMS, how produced by variation and selection, 286. NEW GUINEA, relation of the several Papuan islands to, 194. NOCTURNAL animals, colours of, 51. NOMADA, 98. OBEREA, species resemble Tenthredinidæ, 96. _Odontocera odyneroides_, 96. ODONTOCHEILA, 97. _Odyncrus sinuatus_, 90. _Onthophilus sulcatus_, like a seed, 58. _Onychocerus scorpio_, resembles bark, 56. ORANGE-TIP butterfly, protective colouring of, 59. ORCHIS, structure of an, explained by natural selection, 271. _Orgyia antiqua_ and _O. Gonostigma_, autumnal colours of, 62. ORIOLIDÆ, 253. _Ornithoptera priamus_, 145, 173; _O. Helena_, 173. _Oxyrhopus petolarius_, _O. Trigeminus_, _O. Formosus_, 102. OWEN, Professor, on more generalized structure of extinct animals, 298. _Pachyotris fabricii_, 96. PACHYRHYNCHI, weevils mimicked by Longicorns, 95. PALEOTHERIUM, 299. PALOPLOTHERIUM, 299. PAPILIO, black and red group imitated, 84. _Papilio achates_, 147; _P. Adamantius_, 171; _P. ænigma_, 87; _P. Agamemnon_, 141, 158, 170, 171; _P. Agestor_, 180; _P. Alphenor_, 148, 169; _P. Amanga_, 151; _P. Androcles_, 171; _P. Androgeus_, 88, 147, 180, 183; _P. Antiphates_, 141, 171; _P. Antiphus_, 87, 150, 170, 180, 183; _P. Aristæus_, 171; _P. Arjuna_, 141; _P. Ascalaphus_, 171; _P. Autolycus_, 160; _P. Bathycles_, 141; _P. Blumei_, 171; _P. Brama_, 171; _P. Caunus_, 87, 179; _P. Codrus_, 160, 171; _P. Cöon_, 88, 146, 180, 182; _P. Deiphobus_, 140; _P. Deiphontes_, 171; _P. Delessertii_, 180; _P. Demolion_, 171; _P. Diphilus_, 87, 170, 180, 183; _P. Doubledayi_, 88, 180; _P. Elyros_, 148; _P. Encelades_, 171; _P. Erectheus_, 151; _P. Euripilus_, 160; _P. Evemon_, 159; _P. Gigon_, 171; _P. Glaucus_, 152; _P. Hector_, 87, 150, 180, 183; _P. Helenus_, 160, 171; _P. Hospiton_, 178; _P. Idæoides_, 180; _P. Jason_, 159, 171; _P. Ledebouria_, 148; _P. Leucothoë_, 171; _P. Leodamas_, 170; _P. Liris_, 87, 180, 184; _P. Macareus_, 179; _P. Machaon_, 178; _P. Melanides_, 148, 150; _P. Memnon_, 88, 140, 146, 147, 152, 180, 183; _P. Milon_, 171; _P. Nephelus_, 140; _P. Nicanor_, 170; _P. Oenomaus_, 88, 180, 184; _P. Onesimus_, 151; _P. Ormenus_, 150, 152, 182; _P. Pammon_, 147, 152, 170, 180; _P. Pamphylus_, 171; _P. Pandion_, 152, 180; _P. Paradoxa_, 87, 179; _P. Peranthus_, 160, 171; _P. Pertinax_, 145; _P. Philoxenus_, 182; _P. Polydorus_, 88, 170, 182; _P. Polytes_, 147, 148; _P. Rhesus_, 171; _P. Romulus_, 87, 148, 150, 183; _P. Sarpedon_, 141, 158, 171; _P. Sataspes_, 171; _P. Severus_, 140, 144; _P. Theseus_, 87, 148, 150, 169, 170, 171, 180, 183; _P. Thule_, 179; _P. Torquatus_, 156; _P. Turnus_, 152; _P. Ulysses_, 140, 160, 173; _P. Varuna_, 88. PAPILIONIDÆ, the question of their rank, 133; peculiar characters possessed by, 134; peculiarly diurnal, 136; compared with groups of mammalia, 138; distribution of, 140; large forms of Celebes and Moluccas, 168; large forms of Amboyna, 169; local variation of form, 169; arrangement of, 186; geographical distribution of, 189; of Indo-Malay and Austro-Malay regions, 192; of Java, Sumatra, and Borneo, 193. PARIDÆ, sexual colouring and nidification of, 243. PASSENGER pigeon, cause of its great numbers, 308. PATENT inventions, as illustrating classification, 295. _Phacellocera batesii_, mimics one of the Anthribidæ, 94. _Phalaropus fulicarius_, 115, 251. PHASMIDÆ, imitate sticks and twigs, 64; females resembling leaves, 112. PHYLLIUM, wonderful protective colour and form of, 64. PHYSALIA, 258. PIERIDÆ, local modification of form in, 172. PIERIS, females only imitating Heliconidæ, 112. _Pieris coronis_, 172; _eperia_, 172. _Pieris pyrrha_, 113. PICIDÆ, sexual colouring and nidification of, 242. PIPRIDÆ, sexual colouring and nidification of, 245. PITTIDÆ, 253. _Pliocerus equalis_, 101; _P. Elapoides, P. Euryzonus_, 102. _Pæciloderma terminale_, 93. POLARITY, Forbes' theory of, 17, 45. POLYMORPHISM, 145; illustration of, 157. POPULATION of species, law of, 28; does not permanently increase, 29; not determined by abundance of offspring, 29; checks to, 30; difference in the case of cats and rabbits explained, 32. PREVISION, a case of, 122. PRIONITURUS, 196. PROTECTION, various modes in which animals obtain it, 69-71, 258; greater need of, in female insects and birds, 113. PROTECTIVE colouring, theory of, 65. PSITTACI (Parrots), sexual colouring and nidification of, 242. PTEROSAURIA, 298. PTYCHODERES, 94. RACES, or subspecies, 160; of man, origin of, 319. REDBREAST and woodpigeon, protective colouring of, 53, 54. REPRESENTATIVE groups, 9; of Trogons, butterflies, &c. , 12. REPTILES, protective colouring of, 54. RHAMPHASTIDÆ, sexual colouring and nidification of, 242. RHINOCEROS, 299. RIVER system, as illustrating self-adaptation, 276. ROSES, Mr. Baker on varieties of, 165. RUDIMENTARY organs, 23. SALVIN, Mr. Osbert, on a case of bird mimicry, 107. _Saturnia pavonia-minor_, protective colouring of larva of, 63. SATYRIDÆ, probable means of protection of, 176. SAUROPTERYGIA, 299. SAVAGES, why they become extinct, 319; undeveloped intellect of, 339, 341; intellect of, compared with that of animals, 341, 343; protect their backs from rain, 346. SCANSORIAL birds, nests of, 238. SCAPHURA, 98. SCISSIROSTRUM, 165. SCOPULIPEDES, brush-legged bees, 91. SCUDDER, Mr. , on fossil insects, 301. SCUTELLERIDÆ, mimicked by Longicorns, 96. _Sesia bombiliformis_, 90. SESIIDÆ, mimic Hymenoptera, 90. SEXES, comparative importance of, in different classes of animals, 111; diverse habits of, 156. SEXUAL SELECTION, 156; its normal action to develop colour in both sexes, 247; among birds, 283. SIDGWICK, Mr. A. , on protective colouring of moths, 62. SIMOCYONIDÆ, 300. SITTA, sexual colouring and nidification of, 243. SITTELLA, sexual colouring and nidification of, 243. SNAKES, mimicry among, 101. SONG of birds, instinctive or imitative, 220. SPECIES, law of population of, 28; abundance or rarity of, dependent on the adaptation to conditions, 33; definition of, 141, 161; the range and constancy of, 143; extreme variation in, 163, 164. SPEED of animals, limits of, 292. _Sphecia craboniforme_, 90. _Sphecomorpha chalybea_, 96. SPHEGIDÆ, mimicked by flies, 97. SPIDERS, which mimic ants, 98; and flower buds, 99. _Spilosoma menthastri_, 88. STAINTON, Mr. , on moths rejected by turkeys, 78, 88. STALACHTIS, a genus of Erycinidæ, the object of mimicry, 84. STINGING insects generally conspicuously coloured, 72. STREPTOCITTA, 196. STURNIDÆ, sexual colouring and nidification of, 244. STURNOPASTOR, 239. ST. HELENA, 10. _Streptolabis hispoides_, 93. STRUGGLE for existence, 28, 33. SURVIVAL of the fittest, law of, stated, 33; its action in determining colour, 67. SWAINSON'S circular and quinarian theory, 45. SYLVIADÆ, sexual colouring and nidification of, 245. SYNAPTA, 258. _TACHORNIS phoenicobea_, 228. _Tachyris hombronii_, 172; _ithome_, 172; _lycaste_, 172; _lyncida_, 172; _nephele_, 172; _nero_, 172; _zarinda_, 172. TANAGRIDÆ, sexual colouring and nidification of, 245. TAPIR, 299. TELEPHORI, similar colouring of two sexes, 114. TEMPERATE and cold climates favourable to civilization, 318. THECODONTIA, 299. THERATES, mimicked by Heteromera, 95. _Thyca descombesi_, 172; _hyparete_, 172; _rosenbergii_, 172; _zebuda_, 172. TIGER, adaptive colouring of, 52. TIMES newspaper on Natural Selection, 296. TOOLS, importance of, to man, 314. TREE FROGS, probable mimicry by, 103. TRICONDYLA, 97. TRIMEN, Mr. , on rank of the Papilionidæ, 136. TRISTRAM, Rev. H. , on colours of desert animals, 50. _Trochilium tipuliforme_, 90. TROGONIDÆ, sexual colouring and nidification of, 241. TROPICAL birds often green, 52. TROPICS, most favourable to production of perfect adaptation among animals, 68; not favourable to growth of civilization, 318. TROPIDORHYNCHUS mimicked by orioles, 104. TRUTHFULNESS of some savages, 353; not to be explained on utilitarian hypothesis, 354. TURDIDÆ, sexual colouring and nidification of, 245. TURNIX, 115, 251. TYNDALL, Professor, on origin of consciousness, 361. UPUPIDÆ, sexual colouring and nidification of, 241. USEFUL and useless variations, 34. UTILITY, importance of the principle of, 47, 127. VARIABILITY, simple, 144. VARIATIONS, useful and useless, 34; laws of, 143, 266; as influenced by locality, 166; of size, 168; universality of, 287-291; are there limits to, 291; of domestic dogs, 293; of pigeons, 293. VARIETIES, instability of, supposed to prove the permanent distinctness of species, 26; if superior will extirpate original species, 36; its reversion then impossible, 37; of domesticated animals may partially revert, 38, 40; inconvenience of using the term, 161. VERTEBRATA, mimicry among, 99. VOICE of man, not explained by natural selection, 350. VOLUCELLA, species of mimic bees, 75, 98. WALSH, Mr. , on dimorphism, of _Papilio turnus_, 153. WEAPONS and tools, how they affect man's progress, 314. WEEVILS often resemble small lumps of earth, 58. WEIR, Mr. Jenner, on a moth refused by birds, 89; on beetles refused by birds, 93; on caterpillars eaten and rejected by birds, 119. WESTWOOD, Professor, objections to theory of mimicry, 108. WHITE colour in domesticated and wild animals, 66. WILD and domesticated animals, essential differences of, 38-41. WILL really exerts force, 367; probably the primary source of force, 368. WOOD, Mr. T. W. , on orange-tip butterfly, 59. WOODCOCKS and Snipes, protective colouring of, 53. WOODPECKERS, why scarce in England, 32. _XANTHIA_, autumnal colours of these moths, 62. ZEBRAS, 299. +--------------------------------------------------------------+ | Transcriber's Notes & Errata | | | | The following entries were added to the Table of Contents. | | | | In Chapter IV. --_The Malayan Papilionidæ, or Swallow-tailed | | Butterflies, as illustrative of the Theory of Natural | | Selection. _: | | | | Arrangement and Geographical Distribution of the Malayan | | Papilionidæ | | | | Range of the Groups of Malayan Papilionidæ | | | | | | In Chapter VI. --_The Philosophy of Birds' Nests. _: | | | | How young Birds may learn to build Nests. | | | | | | Missing page number 94 supplied for the entry "_Phacellocera | | batesii_, mimics one of the Anthribidæ, " in the index. | | | | The following words were found in both hyphenated and | | unhyphenated forms (incidence in parentheses). | | | | |Co-existing (2) |Coexisting (1) | | | |Fly-catcher (1) |Flycatcher (2) | | | |sea-weed (2) |seaweed (1) | | | |bull-dog (1) |bulldog (1) | | | | | The following typographical errors have been corrected: | | | | |Error |Correction | | | | | | | | |sparrrow |sparrow | | | |unwieldly |unwieldy | | | |it |its | | | |Perphaps |Perhaps | | | |confimation |confirmation | | | |Pharoahs |Pharaohs | | | |receptable |receptacle | | | |occured |occurred | | | |that that |than that | | +--------------------------------------------------------------+