THE ORIGIN OF SPECIES

[1]

By Thomas H. Huxley

MR. DARWIN'S long-standing and well-earned scientific eminence probablyrenders him indifferent to that social notoriety which passes by thename of success; but if the calm spirit of the philosopher have not yetwholly superseded the ambition and the vanity of the carnal man withinhim, he must be well satisfied with the results of his venture inpublishing the 'Origin of Species'. Overflowing the narrow bounds ofpurely scientific circles, the "species question" divides with Italy andthe Volunteers the attention of general society. Everybody has read Mr. Darwin's book, or, at least, has given an opinion upon its merits ordemerits; pietists, whether lay or ecclesiastic, decry it with the mildrailing which sounds so charitable; bigots denounce it with ignorantinvective; old ladies of both sexes consider it a decidedly dangerousbook, and even savants, who have no better mud to throw, quoteantiquated writers to show that its author is no better than an apehimself; while every philosophical thinker hails it as a veritableWhitworth gun in the armoury of liberalism; and all competentnaturalists and physiologists, whatever their opinions as to theultimate fate of the doctrines put forth, acknowledge that the workin which they are embodied is a solid contribution to knowledge andinaugurates a new epoch in natural history. 

Nor has the discussion of the subject been restrained within the limitsof conversation. When the public is eager and interested, reviewers mustminister to its wants; and the genuine 'litterateur' is too much inthe habit of acquiring his knowledge from the book he judges--as theAbyssinian is said to provide himself with steaks from the ox whichcarries him--to be withheld from criticism of a profound scientific workby the mere want of the requisite preliminary scientific acquirement;while, on the other hand, the men of science who wish well to the newviews, no less than those who dispute their validity, have naturallysought opportunities of expressing their opinions. Hence it is notsurprising that almost all the critical journals have noticed Mr. Darwin's work at greater or less length; and so many disquisitions, of every degree of excellence, from the poor product of ignorance, toooften stimulated by prejudice, to the fair and thoughtful essay ofthe candid student of Nature, have appeared, that it seems an almosthopeless task to attempt to say anything new upon the question. 

But it may be doubted if the knowledge and acumen of prejudgedscientific opponents, or the subtlety of orthodox special pleaders, haveyet exerted their full force in mystifying the real issues of the greatcontroversy which has been set afoot, and whose end is hardly likelyto be seen by this generation; so that, at this eleventh hour, and evenfailing anything new, it may be useful to state afresh that which istrue, and to put the fundamental positions advocated by Mr. Darwin insuch a form that they may be grasped by those whose special studies liein other directions. And the adoption of this course may be the moreadvisable, because, notwithstanding its great deserts, and indeed partlyon account of them, the 'Origin of Species' is by no means an easy bookto read--if by reading is implied the full comprehension of an author'smeaning. 

We do not speak jestingly in saying that it is Mr. Darwin's misfortuneto know more about the question he has taken up than any man living. Personally and practically exercised in zoology, in minute anatomy, in geology; a student of geographical distribution, not on maps andin museums only, but by long voyages and laborious collection; havinglargely advanced each of these branches of science, and having spentmany years in gathering and sifting materials for his present work, the store of accurately registered facts upon which the author of the'Origin of Species' is able to draw at will is prodigious. 

But this very superabundance of matter must have been embarrassing toa writer who, for the present, can only put forward an abstract of hisviews; and thence it arises, perhaps, that notwithstanding the clearnessof the style, those who attempt fairly to digest the book find much ofit a sort of intellectual pemmican--a mass of facts crushed and poundedinto shape, rather than held together by the ordinary medium of anobvious logical bond; due attention will, without doubt, discover thisbond, but it is often hard to find. 

Again, from sheer want of room, much has to be taken for granted whichmight readily enough be proved; and hence, while the adept, who cansupply the missing links in the evidence from his own knowledge, discovers fresh proof of the singular thoroughness with which alldifficulties have been considered and all unjustifiable suppositionsavoided, at every reperusal of Mr. Darwin's pregnant paragraphs, thenovice in biology is apt to complain of the frequency of what he fanciesis gratuitous assumption. 

Thus while it may be doubted if, for some years, any one is likely to becompetent to pronounce judgment on all the issues raised by Mr. Darwin, there is assuredly abundant room for him, who, assuming the humbler, though perhaps as useful, office of an interpreter between the 'Originof Species' and the public, contents himself with endeavouring topoint out the nature of the problems which it discusses; to distinguishbetween the ascertained facts and the theoretical views which itcontains; and finally, to show the extent to which the explanation itoffers satisfies the requirements of scientific logic. At any rate, itis this office which we purpose to undertake in the following pages. 

It may be safely assumed that our readers have a general conception ofthe nature of the objects to which the word "species" is applied; but ithas, perhaps, occurred to a few, even to those who are naturalists 'exprofesso', to reflect, that, as commonly employed, the term has a doublesense and denotes two very different orders of relations. When we call agroup of animals, or of plants, a species, we may imply thereby, eitherthat all these animals or plants have some common peculiarity of formor structure; or, we may mean that they possess some common functionalcharacter. That part of biological science which deals with formand structure is called Morphology--that which concerns itself withfunction, Physiology--so that we may conveniently speak of these twosenses, or aspects, of "species"--the one as morphological, the otheras physiological. Regarded from the former point of view, a speciesis nothing more than a kind of animal or plant, which is distinctlydefinable from all others, by certain constant, and not merely sexual, morphological peculiarities. Thus horses form a species, because thegroup of animals to which that name is applied is distinguished from allothers in the world by the following constantly associated characters. They have--1, A vertebral column; 2, Mammae; 3, A placental embryo; 4, Four legs; 5, A single well-developed toe in each foot provided with ahoof; 6, A bushy tail; and 7, Callosities on the inner sides of boththe fore and the hind legs. The asses, again, form a distinct species, because, with the same characters, as far as the fifth in the abovelist, all asses have tufted tails, and have callosities only on theinner side of the fore-legs. If animals were discovered having thegeneral characters of the horse, but sometimes with callosities onlyon the fore-legs, and more or less tufted tails; or animals having thegeneral characters of the ass, but with more or less bushy tails, and sometimes with callosities on both pairs of legs, besides beingintermediate in other respects--the two species would have to be mergedinto one. They could no longer be regarded as morphologically distinctspecies, for they would not be distinctly definable one from the other. 

However bare and simple this definition of species may appear to be, we confidently appeal to all practical naturalists, whether zoologists, botanists, or palaeontologists, to say if, in the vast majority ofcases, they know, or mean to affirm anything more of the group ofanimals or plants they so denominate than what has just been stated. Even the most decided advocates of the received doctrines respectingspecies admit this. 

"I apprehend, " says Professor Owen [2], "that few naturalists nowadays, in describing and proposing a name for what they call 'a new species, 'use that term to signify what was meant by it twenty or thirty yearsago; that is, an originally distinct creation, maintaining its primitivedistinction by obstructive generative peculiarities. The proposer of thenew species now intends to state no more than he actually knows; as, forexample, that the differences on which he founds the specific characterare constant in individuals of both sexes, so far as observation hasreached; and that they are not due to domestication or to artificiallysuperinduced external circumstances, or to any outward influence withinhis cognizance; that the species is wild, or is such as it appears byNature. "

If we consider, in fact, that by far the largest proportion of recordedexisting species are known only by the study of their skins, or bones, or other lifeless exuvia; that we are acquainted with none, or next tonone, of their physiological peculiarities, beyond those which can bededuced from their structure, or are open to cursory observation; andthat we cannot hope to learn more of any of those extinct forms of lifewhich now constitute no inconsiderable proportion of the known Flora andFauna of the world: it is obvious that the definitions of these speciescan be only of a purely structural, or morphological, character. It isprobable that naturalists would have avoided much confusion of ideasif they had more frequently borne the necessary limitations of ourknowledge in mind. But while it may safely be admitted that we areacquainted with only the morphological characters of the vast majorityof species--the functional or physiological, peculiarities of a few havebeen carefully investigated, and the result of that study forms a largeand most interesting portion of the physiology of reproduction. 

The student of Nature wonders the more and is astonished the less, themore conversant he becomes with her operations; but of all the perennialmiracles she offers to his inspection, perhaps the most worthy ofadmiration is the development of a plant or of an animal from itsembryo. Examine the recently laid egg of some common animal, such as asalamander or newt. It is a minute spheroid in which the best microscopewill reveal nothing but a structureless sac, enclosing a glairy fluid, holding granules in suspension. But strange possibilities lie dormantin that semi-fluid globule. Let a moderate supply of warmth reach itswatery cradle, and the plastic matter undergoes changes so rapid, yetso steady and purposelike in their succession, that one can only comparethem to those operated by a skilled modeller upon a formless lump ofclay. As with an invisible trowel, the mass is divided and subdividedinto smaller and smaller portions, until it is reduced to an aggregationof granules not too large to build withal the finest fabrics of thenascent organism. And, then, it is as if a delicate finger traced outthe line to be occupied by the spinal column, and moulded the contourof the body; pinching up the head at one end, the tail at the other, and fashioning flank and limb into due salamandrine proportions, in soartistic a way, that, after watching the process hour by hour, one isalmost involuntarily possessed by the notion, that some more subtle aidto vision than an achromatic, would show the hidden artist, with hisplan before him, striving with skilful manipulation to perfect his work. 

As life advances, and the young amphibian ranges the waters, the terrorof his insect contemporaries, not only are the nutritious particlessupplied by its prey, by the addition of which to its frame, growthtakes place, laid down, each in its proper spot, and in such dueproportion to the rest, as to reproduce the form, the colour, and thesize, characteristic of the parental stock; but even the wonderfulpowers of reproducing lost parts possessed by these animals arecontrolled by the same governing tendency. Cut off the legs, the tail, the jaws, separately or all together, and, as Spallanzani showed longago, these parts not only grow again, but the redintegrated limb isformed on the same type as those which were lost. The new jaw, or leg, is a newt's, and never by any accident more like that of a frog. What istrue of the newt is true of every animal and of every plant; the acorntends to build itself up again into a woodland giant such as that fromwhose twig it fell; the spore of the humblest lichen reproduces thegreen or brown incrustation which gave it birth; and at the other end ofthe scale of life, the child that resembled neither the paternal nor thematernal side of the house would be regarded as a kind of monster. 

So that the one end to which, in all living beings, the formativeimpulse is tending--the one scheme which the Archaeus of the oldspeculators strives to carry out, seems to be to mould the offspringinto the likeness of the parent. It is the first great law ofreproduction, that the offspring tends to resemble its parent orparents, more closely than anything else. 

Science will some day show us how this law is a necessary consequenceof the more general laws which govern matter; but, for the present, morecan hardly be said than that it appears to be in harmony with them. Weknow that the phenomena of vitality are not something apart from otherphysical phenomena, but one with them; and matter and force are the twonames of the one artist who fashions the living as well as thelifeless. Hence living bodies should obey the same great laws as othermatter--nor, throughout Nature, is there a law of wider application thanthis, that a body impelled by two forces takes the direction of theirresultant. But living bodies may be regarded as nothing but extremelycomplex bundles of forces held in a mass of matter, as the complexforces of a magnet are held in the steel by its coercive force; and, since the differences of sex are comparatively slight, or, in otherwords, the sum of the forces in each has a very similar tendency, theirresultant, the offspring, may reasonably be expected to deviate butlittle from a course parallel to either, or to both. 

Represent the reason of the law to ourselves by what physical metaphoror analogy we will, however, the great matter is to apprehend itsexistence and the importance of the consequences deducible from it. Forthings which are like to the same are like to one another; and if; ina great series of generations, every offspring is like its parent, itfollows that all the offspring and all the parents must be likeone another; and that, given an original parental stock, with theopportunity of undisturbed multiplication, the law in questionnecessitates the production, in course of time, of an indefinitely largegroup, the whole of whose members are at once very similar and are bloodrelations, having descended from the same parent, or pair of parents. The proof that all the members of any given group of animals, or plants, had thus descended, would be ordinarily considered sufficient to entitlethem to the rank of physiological species, for most physiologistsconsider species to be definable as "the offspring of a single primitivestock. "

But though it is quite true that all those groups we call species 'may', according to the known laws of reproduction, have descended from asingle stock, and though it is very likely they really have done so, yet this conclusion rests on deduction and can hardly hope to establishitself upon a basis of observation. And the primitiveness of thesupposed single stock, which, after all, is the essential part of thematter, is not only a hypothesis, but one which has not a shadow offoundation, if by "primitive" he meant "independent of any other livingbeing. " A scientific definition, of which an unwarrantable hypothesisforms an essential part, carries its condemnation within itself;but, even supposing such a definition were, in form, tenable, thephysiologist who should attempt to apply it in Nature would soon findhimself involved in great, if not inextricable, difficulties. As we havesaid, it is indubitable that offspring 'tend' to resemble the parentalorganism, but it is equally true that the similarity attained neveramounts to identity, either in form or in structure. There is always acertain amount of deviation, not only from the precise characters of asingle parent, but when, as in most animals and many plants, the sexesare lodged in distinct individuals, from an exact mean between the twoparents. And indeed, on general principles, this slight deviation seemsas intelligible as the general similarity, if we reflect how complex theco-operating "bundles of forces" are, and how improbable it is that, inany case, their true resultant shall coincide with any mean betweenthe more obvious characters of the two parents. Whatever be its cause, however, the co-existence of this tendency to minor variation with thetendency to general similarity, is of vast importance in its bearing onthe question of the origin of species. 

As a general rule, the extent to which an offspring differs from itsparent is slight enough; but, occasionally, the amount of difference ismuch more strongly marked, and then the divergent offspring receives thename of a Variety. Multitudes, of what there is every reason to believeare such varieties, are known, but the origin of very few has beenaccurately recorded, and of these we will select two as more especiallyillustrative of the main features of variation. The first of them isthat of the "Ancon, " or "Otter" sheep, of which a careful account isgiven by Colonel David Humphreys, F. R. S. , in a letter to Sir JosephBanks, published in the Philosophical Transactions for 1813. It appearsthat one Seth Wright, the proprietor of a farm on the banks of theCharles River, in Massachusetts, possessed a flock of fifteen ewes anda ram of the ordinary kind. In the year 1791, one of the ewes presentedher owner with a male lamb, differing, for no assignable reason, fromits parents by a proportionally long body and short bandy legs, whenceit was unable to emulate its relatives in those sportive leaps over theneighbours' fences, in which they were in the habit of indulging, muchto the good farmer's vexation. 

The second case is that detailed by a no less unexceptionable authoritythan Reaumur, in his 'Art de faire eclore les Poulets'. A Maltesecouple, named Kelleia, whose hands and feet were constructed upon theordinary human model, had born to them a son, Gratio, who possessed sixperfectly movable fingers on each hand, and six toes, not quite so wellformed, on each foot. No cause could be assigned for the appearance ofthis unusual variety of the human species. 

Two circumstances are well worthy of remark in both these cases. Ineach, the variety appears to have arisen in full force, and, as it were, 'per saltum'; a wide and definite difference appearing, at once, betweenthe Ancon ram and the ordinary sheep; between the six-fingered andsix-toed Gratio Kelleia and ordinary men. In neither case is it possibleto point out any obvious reason for the appearance of the variety. Doubtless there were determining causes for these as for all otherphenomena; but they do not appear, and we can be tolerably certain thatwhat are ordinarily understood as changes in physical conditions, as inclimate, in food, or the like, did not take place and had nothing to dowith the matter. It was no case of what is commonly called adaptationto circumstances; but, to use a conveniently erroneous phrase, thevariations arose spontaneously. The fruitless search after final causesleads their pursuers a long way; but even those hardy teleologists, whoare ready to break through all the laws of physics in chase of theirfavourite will-o'-the-wisp, may be puzzled to discover what purposecould be attained by the stunted legs of Seth Wright's ram or thehexadactyle members of Gratio Kelleia. 

Varieties then arise we know not why; and it is more than probable thatthe majority of varieties have arisen in this "spontaneous" manner, though we are, of course, far from denying that they may be traced, in some cases, to distinct external influences; which are assuredlycompetent to alter the character of the tegumentary covering, tochange colour, to increase or diminish the size of muscles, to modifyconstitution, and, among plants, to give rise to the metamorphosis ofstamens into petals, and so forth. But however they may have arisen, what especially interests us at present is, to remark that, once inexistence, varieties obey the fundamental law of reproduction that liketends to produce like; and their offspring exemplify it by tendingto exhibit the same deviation from the parental stock as themselves. Indeed, there seems to be, in many instances, a pre-potent influenceabout a newly-arisen variety which gives it what one may call an unfairadvantage over the normal descendants from the same stock. This isstrikingly exemplified by the case of Gratio Kelleia, who married awoman with the ordinary pentadactyle extremities, and had by herfour children, Salvator, George, Andre, and Marie. Of these childrenSalvator, the eldest boy, had six fingers and six toes, like his father;the second and third, also boys, had five fingers and five toes, like their mother, though the hands and feet of George were slightlydeformed. The last, a girl, had five fingers and five toes, but thethumbs were slightly deformed. The variety thus reproduced itself purelyin the eldest, while the normal type reproduced itself purely in thethird, and almost purely in the second and last: so that it would seem, at first, as if the normal type were more powerful than the variety. But all these children grew up and intermarried with normal wives andhusband, and then, note what took place: Salvator had four children, three of whom exhibited the hexadactyle members of their grandfather andfather, while the youngest had the pentadactyle limbs of the motherand grandmother; so that here, notwithstanding a double pentadactyledilution of the blood, the hexadactyle variety had the best of it. Thesame pre-potency of the variety was still more markedly exemplified inthe progeny of two of the other children, Marie and George. Marie (whosethumbs only were deformed) gave birth to a boy with six toes, and threeother normally formed children; but George, who was not quite so pure apentadactyle, begot, first, two girls, each of whom had six fingersand toes; then a girl with six fingers on each hand and six toes on theright foot, but only five toes on the left; and lastly, a boy with onlyfive fingers and toes. In these instances, therefore, the variety, asit were, leaped over one generation to reproduce itself in full force inthe next. Finally, the purely pentadactyle Andre was the father of manychildren, not one of whom departed from the normal parental type. 

If a variation which approaches the nature of a monstrosity can strivethus forcibly to reproduce itself, it is not wonderful that lessaberrant modifications should tend to be preserved even more strongly;and the history of the Ancon sheep is, in this respect, particularlyinstructive. With the "'cuteness" characteristic of their nation, theneighbours of the Massachusetts farmer imagined it would be an excellentthing if all his sheep were imbued with the stay-at-home tendenciesenforced by Nature upon the newly-arrived ram; and they advised Wrightto kill the old patriarch of his fold, and install the Ancon ram in hisplace. The result justified their sagacious anticipations, and coincidedvery nearly with what occurred to the progeny of Gratio Kelleia. Theyoung lambs were almost always either pure Ancons, or pure ordinarysheep. [3] But when sufficient Ancon sheep were obtained to interbreedwith one another, it was found that the offspring was always pure Ancon. Colonel Humphreys, in fact, states that he was acquainted with only "onequestionable case of a contrary nature. " Here, then, is a remarkableand well-established instance, not only of a very distinct race beingestablished 'per saltum', but of that race breeding "true" at once, andshowing no mixed forms, even when crossed with another breed. 

By taking care to select Ancons of both sexes, for breeding from, itthus became easy to establish an extremely well-marked race; so peculiarthat, even when herded with other sheep, it was noted that the Anconskept together. And there is every reason to believe that the existenceof this breed might have been indefinitely protracted; but theintroduction of the Merino sheep, which were not only very superior tothe Ancons in wool and meat, but quite as quiet and orderly, led to thecomplete neglect of the new breed, so that, in 1813, Colonel Humphreysfound it difficult to obtain the specimen, whose skeleton was presentedto Sir Joseph Banks. We believe that, for many years, no remnant of ithas existed in the United States. 

Gratio Kelleia was not the progenitor of a race of six-fingered men, asSeth Wright's ram became a nation of Ancon sheep, though the tendency ofthe variety to perpetuate itself appears to have been fully as strongin the one case as in the other. And the reason of the difference isnot far to seek. Seth Wright took care not to weaken the Ancon blood bymatching his Ancon ewes with any but males of the same variety, whileGratio Kelleia's sons were too far removed from the patriarchal timesto intermarry with their sisters; and his grandchildren seem not to havebeen attracted by their six-fingered cousins. In other words, in the oneexample a race was produced, because, for several generations, carewas taken to 'select' both parents of the breeding stock from animalsexhibiting a tendency to vary in the same condition; while, in theother, no race was evolved, because no such selection was exercised. A race is a propagated variety; and as, by the laws of reproduction, offspring tend to assume the parental forms, they will be more likely topropagate a variation exhibited by both parents than that possessed byonly one. 

There is no organ of the body of an animal which may not, and does not, occasionally, vary more or less from the normal type; and there isno variation which may not be transmitted and which, if selectivelytransmitted, may not become the foundation of a race. This great truth, sometimes forgotten by philosophers, has long been familiar to practicalagriculturists and breeders; and upon it rest all the methods ofimproving the breeds of domestic animals, which, for the last century, have been followed with so much success in England. Colour, form, size, texture of hair or wool, proportions of various parts, strength orweakness of constitution, tendency to fatten or to remain lean, to givemuch or little milk, speed, strength, temper, intelligence, specialinstincts; there is not one of these characters whose transmission isnot an every-day occurrence within the experience of cattle-breeders, stock-farmers, horse-dealers, and dog and poultry fanciers. Nay, itis only the other day that an eminent physiologist, Dr. Brown-Sequard, communicated to the Royal Society his discovery that epilepsy, artificially produced in guinea-pigs, by a means which he hasdiscovered, is transmitted to their offspring. 

But a race, once produced, is no more a fixed and immutable entity thanthe stock whence it sprang; variations arise among its members, andas these variations are transmitted like any others, new races may bedeveloped out of the pre-existing one 'ad infinitum', or, at least, within any limit at present determined. Given sufficient time andsufficiently careful selection, and the multitude of races whichmay arise from a common stock is as astonishing as are the extremestructural differences which they may present. A remarkable example ofthis is to be found in the rock-pigeon, which Dr. Darwin has, in ouropinion, satisfactorily demonstrated to be the progenitor of all ourdomestic pigeons, of which there are certainly more than a hundredwell-marked races. The most noteworthy of these races are, the fourgreat stocks known to the "fancy" as tumblers, pouters, carriers, andfantails; birds which not only differ most singularly in size, colour, and habits, but in the form of the beak and of the skull: in theproportions of the beak to the skull; in the number of tail-feathers; inthe absolute and relative size of the feet; in the presence or absenceof the uropygial gland; in the number of vertebrae in the back; inshort, in precisely those characters in which the genera and species ofbirds differ from one another. 

And it is most remarkable and instructive to observe, that none of theseraces can be shown to have been originated by the action of changesin what are commonly called external circumstances, upon the wildrock-pigeon. On the contrary, from time immemorial, pigeon-fanciers havehad essentially similar methods of treating their pets, which havebeen housed, fed, protected and cared for in much the same way in allpigeonries. In fact, there is no case better adapted than that ofthe pigeons to refute the doctrine which one sees put forth onhigh authority, that "no other characters than those founded on thedevelopment of bone for the attachment of muscles" are capable ofvariation. In precise contradiction of this hasty assertion, Mr. Darwin's researches prove that the skeleton of the wings in domesticpigeons has hardly varied at all from that of the wild type; while, onthe other hand, it is in exactly those respects, such as the relativelength of the beak and skull, the number of the vertebrae, and thenumber of the tail-feathers, in which muscular exertion can have noimportant influence, that the utmost amount of variation has takenplace. 

We have said that the following out of the properties exhibited byphysiological species would lead us into difficulties, and at this pointthey begin to be obvious; for if, as the result of spontaneous variationand of selective breeding, the progeny of a common stock may becomeseparated into groups distinguished from one another by constant, notsexual, morphological characters, it is clear that the physiologicaldefinition of species is likely to clash with the morphologicaldefinition. No one would hesitate to describe the pouter and the tumbleras distinct species, if they were found fossil, or if their skins andskeletons were imported, as those of exotic wild birds commonlyare--and without doubt, if considered alone, they are good and distinctmorphological species. On the other hand, they are not physiologicalspecies, for they are descended from a common stock, the rock-pigeon. 

Under these circumstances, as it is admitted on all sides that racesoccur in Nature, how are we to know whether any apparently distinctanimals are really of different physiological species, or not, seeingthat the amount of morphological difference is no safe guide? Is thereany test of a physiological species? The usual answer of physiologistsis in the affirmative. It is said that such a test is to be found inthe phenomena of hybridization--in the results of crossing races, ascompared with the results of crossing species. 

So far as the evidence goes at present, individuals, of what arecertainly known to be mere races produced by selection, however distinctthey may appear to be, not only breed freely together, but the offspringof such crossed races are only perfectly fertile with one another. Thus, the spaniel and the greyhound, the dray-horse and the Arab, thepouter and the tumbler, breed together with perfect freedom, and theirmongrels, if matched with other mongrels of the same kind, are equallyfertile. 

On the other hand, there can be no doubt that the individuals ofmany natural species are either absolutely infertile if crossed withindividuals of other species, or, if they give rise to hybrid offspring, the hybrids so produced are infertile when paired together. The horseand the ass, for instance, if so crossed, give rise to the mule, andthere is no certain evidence of offspring ever having been produced by amale and female mule. The unions of the rock-pigeon and thering-pigeon appear to be equally barren of result. Here, then, says thephysiologist, we have a means of distinguishing any two true speciesfrom any two varieties. If a male and a female, selected from eachgroup, produce offspring, and that offspring is fertile with othersproduced in the same way, the groups are races and not species. If, onthe other hand, no result ensues, or if the offspring are infertile withothers produced in the same way, they are true physiological species. The test would be an admirable one, if, in the first place, it werealways practicable to apply it, and if, in the second, it always yieldedresults susceptible of a definite interpretation. Unfortunately, inthe great majority of cases, this touchstone for species is whollyinapplicable. 

The constitution of many wild animals is so altered by confinement thatthey will not breed even with their own females, so that the negativeresults obtained from crosses are of no value; and the antipathy of wildanimals of the same species for one another, or even of wild and tamemembers of the same species, is ordinarily so great, that it is hopelessto look for such unions in Nature. The hermaphrodism of most plants, the difficulty in the way of insuring the absence of their own, or theproper working of other pollen, are obstacles of no less magnitudein applying the test to them. And, in both animals and plants, issuperadded the further difficulty, that experiments must be continuedover a long time for the purpose of ascertaining the fertility of themongrel or hybrid progeny, as well as of the first crosses from whichthey spring. 

Not only do these great practical difficulties lie in the way ofapplying the hybridization test, but even when this oracle can bequestioned, its replies are sometimes as doubtful as those of Delphi. For example, cases are cited by Mr. Darwin, of plants which are morefertile with the pollen of another species than with their own; andthere are others, such as certain 'fuci', whose male element willfertilize the ovule of a plant of distinct species, while the males ofthe latter species are ineffective with the females of the first. Sothat, in the last-named instance, a physiologist, who should cross thetwo species in one way, would decide that they were true species; whileanother, who should cross them in the reverse way, would, with equaljustice, according to the rule, pronounce them to be mere races. Severalplants, which there is great reason to believe are mere varieties, arealmost sterile when crossed; while both animals and plants, which havealways been regarded by naturalists as of distinct species, turn out, when the test is applied, to be perfectly fertile. Again, the sterilityor fertility of crosses seems to bear no relation to the structuralresemblances or differences of the members of any two groups. 

Mr. Darwin has discussed this question with singular ability andcircumspection, and his conclusions are summed up as follows, at page276 of his work:--

"First crosses between forms sufficiently distinct to be ranked asspecies, and their hybrids, are very generally, but not universally, sterile. The sterility is of all degrees, and is often so slight thatthe two most careful experimentalists who have ever lived have come todiametrically opposite conclusions in ranking forms by this test. Thesterility is innately variable in individuals of the same species, andis eminently susceptible of favourable and unfavourable conditions. Thedegree of sterility does not strictly follow systematic affinity, but isgoverned by several curious and complex laws. It is generally differentand sometimes widely different, in reciprocal crosses between the sametwo species. It is not always equal in degree in a first cross, and inthe hybrid produced from this cross. 

"In the same manner as in grafting trees, the capacity of one speciesor variety to take on another is incidental on generally unknowndifferences in their vegetative systems; so in crossing, the greateror less facility of one species to unite with another is incidentalon unknown differences in their reproductive systems. There is no morereason to think that species have been specially endowed with variousdegrees of sterility to prevent them crossing and breeding in Nature, than to think that trees have been specially endowed with various andsomewhat analogous degrees of difficulty in being grafted together, inorder to prevent them becoming inarched in our forests. 

"The sterility of first crosses between pure species, which have theirreproductive systems perfect, seems to depend on several circumstances;in some cases largely on the early death of the embryo. The sterility ofhybrids which have their reproductive systems imperfect, and whichhave had this system and their whole organization disturbed by beingcompounded of two distinct species, seems closely allied to thatsterility which so frequently affects pure species when their naturalconditions of life have been disturbed. This view is supported by aparallelism of another kind: namely, that the crossing of forms, onlyslightly different, is favourable to the vigour and fertility ofthe offspring; and that slight changes in the conditions of life areapparently favourable to the vigour and fertility of all organic beings. It is not surprising that the degree of difficulty in uniting twospecies, and the degree of sterility of their hybrid offspring, shouldgenerally correspond, though due to distinct causes; for both dependon the amount of difference of some kind between the species which arecrossed. Nor is it surprising that the facility of effecting a firstcross, the fertility of hybrids produced from it, and the capacity ofbeing grafted together--though this latter capacity evidently dependson widely different circumstances--should all run to a certain extentparallel with the systematic affinity of the forms which are subjectedto experiment; for systematic affinity attempts to express all kinds ofresemblance between all species. 

"First crosses between forms known to be varieties, or sufficientlyalike to be considered as varieties, and their mongrel offspring, arevery generally, but not quite universally, fertile. Nor is this nearlygeneral and perfect fertility surprising, when we remember how liable weare to argue in a circle with respect to varieties in a state of Nature;and when we remember that the greater number of varieties havebeen produced under domestication by the selection of mere externaldifferences, and not of differences in the reproductive system. Inall other respects, excluding fertility, there is a close generalresemblance between hybrids and mongrels. "--Pp. 276-8. 

We fully agree with the general tenor of this weighty passage; butforcible as are these arguments, and little as the value of fertility orinfertility as a test of species may be, it must not be forgotten thatthe really important fact, so far as the inquiry into the origin ofspecies goes, is, that there are such things in Nature as groups ofanimals and of plants, whose members are incapable of fertile union withthose of other groups; and that there are such things as hybrids, whichare absolutely sterile when crossed with other hybrids. For, if suchphenomena as these were exhibited by only two of those assemblages ofliving objects, to which the name of species (whether it be used in itsphysiological or in its morphological sense) is given, it would haveto be accounted for by any theory of the origin of species, and everytheory which could not account for it would be, so far, imperfect. 

Up to this point, we have been dealing with matters of fact, and thestatements which we have laid before the reader would, to the best ofour knowledge, be admitted to contain a fair exposition of what is atpresent known respecting the essential properties of species, by all whohave studied the question. And whatever may be his theoretical views, nonaturalist will probably be disposed to demur to the following summaryof that exposition:--

Living beings, whether animals or plants, are divisible into multitudesof distinctly definable kinds, which are morphological species. They arealso divisible into groups of individuals, which breed freely together, tending to reproduce their like, and are physiological species. Normallyresembling their parents, the offspring of members of these species arestill liable to vary; and the variation may be perpetuated by selection, as a race, which race, in many cases, presents all the characteristicsof a morphological species. But it is not as yet proved that a raceever exhibits, when crossed with another race of the same species, thosephenomena of hybridization which are exhibited by many species whencrossed with other species. On the other hand, not only is it not provedthat all species give rise to hybrids infertile 'inter se', but thereis much reason to believe that, in crossing, species exhibit everygradation from perfect sterility to perfect fertility. 

Such are the most essential characteristics of species. Even were mannot one of them--a member of the same system and subject to the samelaws--the question of their origin, their causal connexion, that is, with the other phenomena of the universe, must have attracted hisattention, as soon as his intelligence had raised itself above the levelof his daily wants. 

Indeed history relates that such was the case, and has embalmed for usthe speculations upon the origin of living beings, which were among theearliest products of the dawning intellectual activity of man. In thoseearly days positive knowledge was not to be had, but the cravingafter it needed, at all hazards, to be satisfied, and according to thecountry, or the turn of thought, of the speculator, the suggestion thatall living things arose from the mud of the Nile, from a primevalegg, or from some more anthropomorphic agency, afforded a sufficientresting-place for his curiosity. The myths of Paganism are as dead asOsiris or Zeus, and the man who should revive them, in opposition to theknowledge of our time, would be justly laughed to scorn; but the coevalimaginations current among the rude inhabitants of Palestine, recordedby writers whose very name and age are admitted by every scholar to beunknown, have unfortunately not yet shared their fate, but, even atthis day, are regarded by nine-tenths of the civilized world as theauthoritative standard of fact and the criterion of the justice ofscientific conclusions, in all that relates to the origin of things, and, among them, of species. In this nineteenth century, as at the dawnof modern physical science, the cosmogony of the semi-barbarous Hebrewis the incubus of the philosopher and the opprobrium of the orthodox. Who shall number the patient and earnest seekers after truth, from thedays of Galileo until now, whose lives have been embittered and theirgood name blasted by the mistaken zeal of Bibliolaters? Who shall countthe host of weaker men whose sense of truth has been destroyed in theeffort to harmonize impossibilities--whose life has been wasted in theattempt to force the generous new wine of Science into the old bottlesof Judaism, compelled by the outcry of the same strong party?

It is true that if philosophers have suffered, their cause has beenamply avenged. Extinguished theologians lie about the cradle of everyscience as the strangled snakes beside that of Hercules; and historyrecords that whenever science and orthodoxy have been fairly opposed, the latter has been forced to retire from the lists, bleeding andcrushed if not annihilated; scotched, if not slain. But orthodoxy is theBourbon of the world of thought. It learns not, neither can it forget;and though, at present, bewildered and afraid to move, it is as willingas ever to insist that the first chapter of Genesis contains thebeginning and the end of sound science; and to visit, with such pettythunderbolts as its half-paralysed hands can hurl, those who refuse todegrade Nature to the level of primitive Judaism. 

Philosophers, on the other hand, have no such aggressive tendencies. With eyes fixed on the noble goal to which "per aspera et ardua" theytend, they may, now and then, be stirred to momentary wrath by theunnecessary obstacles with which the ignorant, or the malicious, encumber, if they cannot bar, the difficult path; but why should theirsouls be deeply vexed? The majesty of Fact is on their side, and theelemental forces of Nature are working for them. Not a star comes to themeridian at its calculated time but testifies to the justice of theirmethods--their beliefs are "one with falling rain and with the growingcorn. " By doubt they are established, and open inquiry is their bosomfriend. Such men have no fear of traditions however venerable, and norespect for them when they become mischievous and obstructive; but theyhave better than mere antiquarian business in hand, and if dogmas, whichought to be fossil but are not, are not forced upon their notice, theyare too happy to treat them as non-existent. 

The hypotheses respecting the origin of species which profess to standupon a scientific basis, and, as such, alone demand serious attention, are of two kinds. The one, the "special creation" hypothesis, presumesevery species to have originated from one or more stocks, these notbeing the result of the modification of any other form of livingmatter--or arising by natural agencies--but being produced, as such, bya supernatural creative act. 

The other, the so-called "transmutation" hypothesis, considers thatall existing species are the result of the modification of pre-existingspecies, and those of their predecessors, by agencies similar to thosewhich at the present day produce varieties and races, and therefore inan altogether natural way; and it is a probable, though not a necessaryconsequence of this hypothesis, that all living beings have arisen froma single stock. With respect to the origin of this primitive stock, or stocks, the doctrine of the origin of species is obviously notnecessarily concerned. The transmutation hypothesis, for example, isperfectly consistent either with the conception of a special creation ofthe primitive germ, or with the supposition of its having arisen, as amodification of inorganic matter, by natural causes. 

The doctrine of special creation owes its existence very largely to thesupposed necessity of making science accord with the Hebrew cosmogony;but it is curious to observe that, as the doctrine is at presentmaintained by men of science, it is as hopelessly inconsistent with theHebrew view as any other hypothesis. 

If there be any result which has come more clearly out of geologicalinvestigation than another, it is, that the vast series of extinctanimals and plants is not divisible, as it was once supposed to be, intodistinct groups, separated by sharply-marked boundaries. There are nogreat gulfs between epochs and formations--no successive periods markedby the appearance of plants, of water animals, and of land animals, 'en masse'. Every year adds to the list of links between what the oldergeologists supposed to be widely separated epochs: witness the cragslinking the drift with older tertiaries; the Maestricht beds linking thetertiaries with the chalk; the St. Cassian beds exhibiting an abundantfauna of mixed mesozoic and palaeozoic types, in rocks of an epoch oncesupposed to be eminently poor in life; witness, lastly, the incessantdisputes as to whether a given stratum shall be reckoned devonian orcarboniferous, silurian or devonian, cambrian or silurian. 

This truth is further illustrated in a most interesting manner bythe impartial and highly competent testimony of M. Pictet, from whosecalculations of what percentage of the genera of animals, existing inany formation, lived during the preceding formation, it results that inno case is the proportion less than 'one-third', or 33 per cent. It isthe triassic formation, or the commencement of the mesozoic epoch, whichhas received the smallest inheritance from preceding ages. The otherformations not uncommonly exhibit 60, 80, or even 94 per cent. Of generain common with those whose remains are imbedded in their predecessor. Not only is this true, but the subdivisions of each formation exhibitnew species characteristic of, and found only in, them; and, inmany cases, as in the lias for example, the separate beds of thesesubdivisions are distinguished by well-marked and peculiar forms oflife. A section, a hundred feet thick, will exhibit, at differentheights, a dozen species of ammonite, none of which passes beyond itsparticular zone of limestone, or clay, into the zone below it or intothat above it; so that those who adopt the doctrine of special creationmust be prepared to admit, that at intervals of time, corresponding withthe thickness of these beds, the Creator thought fit to interfere withthe natural course of events for the purpose of making a new ammonite. It is not easy to transplant oneself into the frame of mind of those whocan accept such a conclusion as this, on any evidence short of absolutedemonstration; and it is difficult to see what is to be gained by sodoing, since, as we have said, it is obvious that such a view of theorigin of living beings is utterly opposed to the Hebrew cosmogony. Deserving no aid from the powerful arm of Bibliolatry, then, does thereceived form of the hypothesis of special creation derive any supportfrom science or sound logic? Assuredly not much. The argumentsbrought forward in its favour all take one form: If species were notsupernaturally created, we cannot understand the facts 'x' or 'y', or'z'; we cannot understand the structure of animals or plants, unless wesuppose they were contrived for special ends; we cannot understand thestructure of the eye, except by supposing it to have been made to seewith; we cannot understand instincts, unless we suppose animals to havebeen miraculously endowed with them. 

As a question of dialectics, it must be admitted that this sort ofreasoning is not very formidable to those who are not to be frightenedby consequences. It is an 'argumentum ad ignorantiam'--take thisexplanation or be ignorant. 

But suppose we prefer to admit our ignorance rather than adopt ahypothesis at variance with all the teachings of Nature? Or, suppose fora moment we admit the explanation, and then seriously ask ourselves howmuch the wiser are we; what does the explanation explain? Is it any morethan a grandiloquent way of announcing the fact, that we really knownothing about the matter? A phenomenon is explained when it is shownto be a case of some general law of Nature; but the supernaturalinterposition of the Creator can, by the nature of the case, exemplifyno law, and if species have really arisen in this way, it is absurd toattempt to discuss their origin. 

Or, lastly, let us ask ourselves whether any amount of evidence whichthe nature of our faculties permits us to attain, can justify us inasserting that any phenomenon is out of the reach of natural causation. To this end it is obviously necessary that we should know all theconsequences to which all possible combinations, continued throughunlimited time, can give rise. If we knew these, and found nonecompetent to originate species, we should have good ground for denyingtheir origin by natural causation. Till we know them, any hypothesis isbetter than one which involves us in such miserable presumption. 

But the hypothesis of special creation is not only a mere speciousmask for our ignorance; its existence in Biology marks the youth andimperfection of the science. For what is the history of every sciencebut the history of the elimination of the notion of creative, or otherinterferences, with the natural order of the phenomena which are thesubject-matter of that science? When Astronomy was young "the morningstars sang together for joy, " and the planets were guided in theircourses by celestial hands. Now, the harmony of the stars has resolveditself into gravitation according to the inverse squares of thedistances, and the orbits of the planets are deducible from the lawsof the forces which allow a schoolboy's stone to break a window. Thelightning was the angel of the Lord; but it has pleased Providence, inthese modern times, that science should make it the humble messenger ofman, and we know that every flash that shimmers about the horizon on asummer's evening is determined by ascertainable conditions, and thatits direction and brightness might, if our knowledge of these were greatenough, have been calculated. 

The solvency of great mercantile companies rests on the validity of thelaws which have been ascertained to govern the seeming irregularityof that human life which the moralist bewails as the most uncertain ofthings; plague, pestilence, and famine are admitted, by all but fools, to be the natural result of causes for the most part fully withinhuman control, and not the unavoidable tortures inflicted by wrathfulOmnipotence upon His helpless handiwork. 

Harmonious order governing eternally continuous progress--the web andwoof of matter and force interweaving by slow degrees, without a brokenthread, that veil which lies between us and the Infinite--that universewhich alone we know or can know; such is the picture which science drawsof the world, and in proportion as any part of that picture is in unisonwith the rest, so may we feel sure that it is rightly painted. ShallBiology alone remain out of harmony with her sister sciences?

Such arguments against the hypothesis of the direct creation of speciesas these are plainly enough deducible from general considerations; butthere are, in addition, phenomena exhibited by species themselves, andyet not so much a part of their very essence as to have required earliermention, which are in the highest degree perplexing, if we adopt thepopularly accepted hypothesis. Such are the facts of distribution inspace and in time; the singular phenomena brought to light by the studyof development; the structural relations of species upon whichour systems of classification are founded; the great doctrines ofphilosophical anatomy, such as that of homology, or of the communityof structural plan exhibited by large groups of species differing verywidely in their habits and functions. 

The species of animals which inhabit the sea on opposite sides of theisthmus of Panama are wholly distinct [4] the animals and plants whichinhabit islands are commonly distinct from those of the neighbouringmainlands, and yet have a similarity of aspect. 

The mammals of the latest tertiary epoch in the Old and New Worldsbelong to the same genera, or family groups, as those which now inhabitthe same great geographical area. The crocodilian reptiles which existedin the earliest secondary epoch were similar in general structure tothose now living, but exhibit slight differences in their vertebrae, nasal passages, and one or two other points. The guinea-pig has teethwhich are shed before it is born, and hence can never subserve themasticatory purpose for which they seem contrived, and, in like manner, the female dugong has tusks which never cut the gum. All the membersof the same great group run through similar conditions in theirdevelopment, and all their parts, in the adult state, are arrangedaccording to the same plan. Man is more like a gorilla than a gorilla islike a lemur. Such are a few, taken at random, among the multitudesof similar facts which modern research has established; but when thestudent seeks for an explanation of them from the supporters of thereceived hypothesis of the origin of species, the reply he receivesis, in substance, of Oriental simplicity and brevity--"Mashallah! itso pleases God!" There are different species on opposite sides of theisthmus of Panama, because they were created different on the two sides. The pliocene mammals are like the existing ones, because such was theplan of creation; and we find rudimental organs and similarity of plan, because it has pleased the Creator to set before Himself a "divineexemplar or archetype, " and to copy it in His works; and somewhatill, those who hold this view imply, in some of them. That such verbalhocus-pocus should be received as science will one day be regarded asevidence of the low state of intelligence in the nineteenth century, just as we amuse ourselves with the phraseology about Nature'sabhorrence of a vacuum, wherewith Torricelli's compatriots weresatisfied to explain the rise of water in a pump. And be it recollectedthat this sort of satisfaction works not only negative but positive ill, by discouraging inquiry, and so depriving man of the usufruct of one ofthe most fertile fields of his great patrimony, Nature. 

The objections to the doctrine of the origin of species by specialcreation which have been detailed, must have occurred, with more orless force, to the mind of every one who has seriously and independentlyconsidered the subject. It is therefore no wonder that, from time totime, this hypothesis should have been met by counter hypotheses, all aswell, and some better founded than itself; and it is curious to remarkthat the inventors of the opposing views seem to have been led into themas much by their knowledge of geology, as by their acquaintance withbiology. In fact, when the mind has once admitted the conception ofthe gradual production of the present physical state of our globe, bynatural causes operating through long ages of time, it will be littledisposed to allow that living beings have made their appearance inanother way, and the speculations of De Maillet and his successors arethe natural complement of Scilla's demonstration of the true nature offossils. 

A contemporary of Newton and of Leibnitz, sharing therefore in theintellectual activity of the remarkable age which witnessed the birthof modern physical science, Benoit de Maillet spent a long life as aconsular agent of the French Government in various Mediterranean ports. For sixteen years, in fact, he held the office of Consul-General inEgypt, and the wonderful phenomena offered by the valley of the Nileappear to have strongly impressed his mind, to have directed hisattention to all facts of a similar order which came within hisobservation, and to have led him to speculate on the origin of thepresent condition of our globe and of its inhabitants. But, with all hisardour for science, De Maillet seems to have hesitated to publish viewswhich, notwithstanding the ingenious attempts to reconcile them with theHebrew hypothesis contained in the preface to "Telliamed, " were hardlylikely to be received with favour by his contemporaries. 

But a short time had elapsed since more than one of the great anatomistsand physicists of the Italian school had paid dearly for theirendeavours to dissipate some of the prevalent errors; and theirillustrious pupil, Harvey, the founder of modern physiology, had notfared so well, in a country less oppressed by the benumbing influencesof theology, as to tempt any man to follow his example. Probablynot uninfluenced by these considerations, his Catholic majesty'sConsul-General for Egypt kept his theories to himself throughout a longlife, for 'Telliamed, ' the only scientific work which is known to haveproceeded from his pen, was not printed till 1735, when its author hadreached the ripe age of seventy-nine; and though De Maillet lived threeyears longer, his book was not given to the world before 1748. Even thenit was anonymous to those who were not in the secret of the anagrammaticcharacter of its title; and the preface and dedication are so worded as, in case of necessity, to give the printer a fair chance of falling backon the excuse that the work was intended for a mere 'jeu d'esprit'. 

The speculations of the suppositious Indian sage, though quite as soundas those of many a "Mosaic Geology, " which sells exceedingly well, haveno great value if we consider them by the light of modern science. Thewaters are supposed to have originally covered the whole globe; to havedeposited the rocky masses which compose its mountains by processescomparable to those which are now forming mud, sand, and shingle; andthen to have gradually lowered their level, leaving the spoils of theiranimal and vegetable inhabitants embedded in the strata. As the dry landappeared, certain of the aquatic animals are supposed to have taken toit, and to have become gradually adapted to terrestrial and aerialmodes of existence. But if we regard the general tenor and style ofthe reasoning in relation to the state of knowledge of the day, twocircumstances appear very well worthy of remark. The first, that DeMaillet had a notion of the modifiability of living forms (thoughwithout any precise information on the subject), and how suchmodifiability might account for the origin of species; the second, thathe very clearly apprehended the great modern geological doctrine, so strongly insisted upon by Hutton, and so ably and comprehensivelyexpounded by Lyell, that we must look to existing causes for theexplanation of past geological events. Indeed, the following passageof the preface, in which De Maillet is supposed to speak of the Indianphilosopher Telliamed, his 'alter ego', might have been written by themost philosophical uniformitarian of the present day:--

"Ce qu'il y a d'etonnant, est que pour arriver a ces connoissances ilsemble avoir perverti l'ordre naturel, puisqu'au lieu de s'attacherd'abord a rechercher l'origine de notre globe il a commence partravailler a s'instruire de la nature. Mais a l'entendre, cerenversement de l'ordre a ete pour lui l'effet d'un genie favorablequi l'a conduit pas a pas et comme par la main aux decouvertes les plussublimes. C'est en decomposant la substance de ce globe par une anatomieexacte de toutes ses parties qu'il a premierement appris de quellesmatieres il etait compose et quels arrangemens ces memes matieresobservaient entre elles. Ces lumieres jointes a l'esprit de comparaisontoujours necessaire a quiconque entreprend de percer les voiles dontla nature aime a se cacher, ont servi de guide a notre philosophe pourparvenir a des connoissances plus interessantes. Par la matiere etl'arrangement de ces compositions il pretend avoir reconnu quelle est laveritable origine de ce globe que nous habitons, comment et par qui il aete forme. "--Pp. Xix. Xx. 

But De Maillet was before his age, and as could hardly fail to happento one who speculated on a zoological and botanical question beforeLinnaeus, and on a physiological problem before Haller, he fell intogreat errors here and there; and hence, perhaps, the general neglect ofhis work. Robinet's speculations are rather behind, than in advanceof, those of De Maillet; and though Linnaeus may have played withthe hypothesis of transmutation, it obtained no serious supportuntil Lamarck adopted it, and advocated it with great ability in his'Philosophie Zoologique. '

Impelled towards the hypothesis of the transmutation of species, partly by his general cosmological and geological views; partly by theconception of a graduated, though irregularly branching, scale of being, which had arisen out of his profound study of plants and of the lowerforms of animal life, Lamarck, whose general line of thought oftenclosely resembles that of De Maillet, made a great advance upon thecrude and merely speculative manner in which that writer deals withthe question of the origin of living beings, by endeavouring to findphysical causes competent to effect that change of one species intoanother, which De Maillet had only supposed to occur. And Lamarckconceived that he had found in Nature such causes, amply sufficient forthe purpose in view. It is a physiological fact, he says, that organsare increased in size by action, atrophied by inaction; it is anotherphysiological fact that modifications produced are transmissible tooffspring. Change the actions of an animal, therefore, and you willchange its structure, by increasing the development of the parts newlybrought into use and by the diminution of those less used; but byaltering the circumstances which surround it you will alter its actions, and hence, in the long run, change of circumstance must producechange of organization. All the species of animals, therefore, are, in Lamarck's view, the result of the indirect action of changes ofcircumstance, upon those primitive germs which he considered to haveoriginally arisen, by spontaneous generation, within the waters of theglobe. It is curious, however, that Lamarck should insist so strongly[5] as he has done, that circumstances never in any degree directlymodify the form or the organization of animals, but only operate bychanging their wants and consequently their actions; for he therebybrings upon himself the obvious question, how, then, do plants, whichcannot be said to have wants or actions, become modified? To thishe replies, that they are modified by the changes in their nutritiveprocesses, which are effected by changing circumstances; and it does notseem to have occurred to him that such changes might be as well supposedto take place among animals. 

When we have said that Lamarck felt that mere speculation was not theway to arrive at the origin of species, but that it was necessary, in order to the establishment of any sound theory on the subject, todiscover by observation or otherwise, some 'vera causa', competent togive rise to them; that he affirmed the true order of classification tocoincide with the order of their development one from another; that heinsisted on the necessity of allowing sufficient time, very strongly;and that all the varieties of instinct and reason were traced back byhim to the same cause as that which has given rise to species, we haveenumerated his chief contributions to the advance of the question. Onthe other hand, from his ignorance of any power in Nature competent tomodify the structure of animals, except the development of parts, oratrophy of them, in consequence of a change of needs, Lamarck was ledto attach infinitely greater weight than it deserves to this agency, and the absurdities into which he was led have met with deservedcondemnation. Of the struggle for existence, on which, as we shall see, Mr. Darwin lays such great stress, he had no conception; indeed, hedoubts whether there really are such things as extinct species, unlessthey be such large animals as may have met their death at the hands ofman; and so little does he dream of there being any other destructivecauses at work, that, in discussing the possible existence of fossilshells, he asks, "Pourquoi d'ailleurs seroient-ils perdues des quel'homme n'a pu operer leur destruction?" ('Phil. Zool. , ' vol. I. P. 77. )Of the influence of selection Lamarck has as little notion, and he makesno use of the wonderful phenomena which are exhibited by domesticatedanimals, and illustrate its powers. The vast influence of Cuvier wasemployed against the Lamarckian views, and, as the untenability ofsome of his conclusions was easily shown, his doctrines sank under theopprobrium of scientific, as well as of theological, heterodoxy. Nor have the efforts made of late years to revive them tended tore-establish their credit in the minds of sound thinkers acquainted withthe facts of the case; indeed it may be doubted whether Lamarck has notsuffered more from his friends than from his foes. 

Two years ago, in fact, though we venture to question if even thestrongest supporters of the special creation hypothesis had not, nowand then, an uneasy consciousness that all was not right, their positionseemed more impregnable than ever, if not by its own inherent strength, at any rate by the obvious failure of all the attempts which had beenmade to carry it. On the other hand, however much the few, who thoughtdeeply on the question of species, might be repelled by the generallyreceived dogmas, they saw no way of escaping from them save by theadoption of suppositions so little justified by experiment or byobservation as to be at least equally distasteful. 

The choice lay between two absurdities and a middle condition of uneasyscepticism; which last, however unpleasant and unsatisfactory, wasobviously the only justifiable state of mind under the circumstances. 

Such being the general ferment in the minds of naturalists, it is nowonder that they mustered strong in the rooms of the Linnaean Society, on the 1st of July of the year 1858, to hear two papers by authorsliving on opposite sides of the globe, working out their resultsindependently, and yet professing to have discovered one and the samesolution of all the problems connected with species. The one of theseauthors was an able naturalist, Mr. Wallace, who had been employed forsome years in studying the productions of the islands of the IndianArchipelago, and who had forwarded a memoir embodying his views toMr. Darwin, for communication to the Linnaean Society. On perusing theessay, Mr. Darwin was not a little surprised to find that it embodiedsome of the leading ideas of a great work which he had been preparingfor twenty years, and parts of which, containing a development of thevery same views, had been perused by his private friends fifteen orsixteen years before. Perplexed in what manner to do full justice bothto his friend and to himself, Mr. Darwin placed the matter in the handsof Dr. Hooker and Sir Charles Lyell, by whose advice he communicateda brief abstract of his own views to the Linnaean Society, at the sametime that Mr. Wallace's paper was read. Of that abstract, the work onthe 'Origin of Species' is an enlargement; but a complete statement ofMr. Darwin's doctrine is looked for in the large and well-illustratedwork which he is said to be preparing for publication. 

The Darwinian hypothesis has the merit of being eminently simple andcomprehensible in principle, and its essential positions may be statedin a very few words: all species have been produced by the developmentof varieties from common stocks; by the conversion of these, first intopermanent races and then into new species, by the process of 'naturalselection', which process is essentially identical with that artificialselection by which man has originated the races of domestic animals--the'struggle for existence' taking the place of man, and exerting, in thecase of natural selection, that selective action which he performs inartificial selection. 

The evidence brought forward by Mr. Darwin in support of his hypothesisis of three kinds. First, he endeavours to prove that species may beoriginated by selection; secondly, he attempts to show that naturalcauses are competent to exert selection; and thirdly, he tries to provethat the most remarkable and apparently anomalous phenomena exhibited bythe distribution, development, and mutual relations of species, can beshown to be deducible from the general doctrine of their origin, whichhe propounds, combined with the known facts of geological change; andthat, even if all these phenomena are not at present explicable by it, none are necessarily inconsistent with it. 

There cannot be a doubt that the method of inquiry which Mr. Darwinhas adopted is not only rigorously in accordance with the canons ofscientific logic, but that it is the only adequate method. Criticsexclusively trained in classics or in mathematics, who have neverdetermined a scientific fact in their lives by induction from experimentor observation, prate learnedly about Mr. Darwin's method, which is notinductive enough, not Baconian enough, forsooth, for them. But even ifpractical acquaintance with the process of scientific investigationis denied them, they may learn, by the perusal of Mr. Mill's admirablechapter "On the Deductive Method, " that there are multitudes ofscientific inquiries in which the method of pure induction helps theinvestigator but a very little way. 

"The mode of investigation, " says Mr. Mill, "which, from the provedinapplicability of direct methods of observation and experiment, remainsto us as the main source of the knowledge we possess, or can acquire, respecting the conditions and laws of recurrence of the more complexphenomena, is called, in its most general expression, the deductivemethod, and consists of three operations: the first, one ofdirect induction; the second, of ratiocination; and the third, ofverification. "

Now, the conditions which have determined the existence of species arenot only exceedingly complex, but, so far as the great majority ofthem are concerned, are necessarily beyond our cognizance. But what Mr. Darwin has attempted to do is in exact accordance with the rule laiddown by Mr. Mill; he has endeavoured to determine certain great factsinductively, by observation and experiment; he has then reasoned fromthe data thus furnished; and lastly, he has tested the validity of hisratiocination by comparing his deductions with the observed facts ofNature. Inductively, Mr. Darwin endeavours to prove that species arisein a given way. Deductively, he desires to show that, if they arise inthat way, the facts of distribution, development, classification, etc. , may be accounted for, 'i. E. ' may be deduced from their mode of origin, combined with admitted changes in physical geography and climate, duringan indefinite period. And this explanation, or coincidence of observedwith deduced facts, is, so far as it extends, a verification of theDarwinian view. 

There is no fault to be found with Mr. Darwin's method, then; but it isanother question whether he has fulfilled all the conditions imposed bythat method. Is it satisfactorily proved, in fact, that species maybe originated by selection? that there is such a thing as naturalselection? that none of the phenomena exhibited by species areinconsistent with the origin of species in this way? If these questionscan be answered in the affirmative, Mr. Darwin's view steps out of therank of hypotheses into those of proved theories; but, so long as theevidence at present adduced falls short of enforcing that affirmation, so long, to our minds, must the new doctrine be content to remain amongthe former--an extremely valuable, and in the highest degree probable, doctrine, indeed the only extant hypothesis which is worth anything in ascientific point of view; but still a hypothesis, and not yet the theoryof species. 

After much consideration, and with assuredly no bias against Mr. Darwin's views, it is our clear conviction that, as the evidence stands, it is not absolutely proven that a group of animals, having all thecharacters exhibited by species in Nature, has ever been originateby selection, whether artificial or natural. Groups having themorphological character of species, distinct and permanent racesin fact, have been so produced over and over again; but there isno positive evidence, at present, that any group of animals has, byvariation and selective breeding, given rise to another group whichwas, even in the least degree, infertile with the first. Mr. Darwin isperfectly aware of this weak point, and brings forward a multitudeof ingenious and important arguments to diminish the force of theobjection. We admit the value of these arguments to their fullestextent; nay, we will go so far as to express our belief thatexperiments, conducted by a skilful physiologist, would very probablyobtain the desired production of mutually more or less infertile breedsfrom a common stock, in a comparatively few years; but still, as thecase stands at present, this "little rift within the lute" is not to bedisguised nor overlooked. 

In the remainder of Mr. Darwin's argument our own private ingenuityhas not hitherto enabled us to pick holes of any great importance; andjudging by what we hear and read, other adventurers in the same fielddo not seem to have been much more fortunate. It has been urged, forinstance, that in his chapters on the struggle for existence and onnatural selection, Mr. Darwin does not so much prove that naturalselection does occur, as that it must occur; but, in fact, no other sortof demonstration is attainable. A race does not attract our attentionin Nature until it has, in all probability, existed for a considerabletime, and then it is too late to inquire into the conditions of itsorigin. Again, it is said that there is no real analogy between theselection which takes place under domestication, by human influence, and any operation which can be effected by Nature, for man interferesintelligently. Reduced to its elements, this argument implies that aneffect produced with trouble by an intelligent agent must, 'a fortiori', be more troublesome, if not impossible, to an unintelligent agent. Evenputting aside the question whether Nature, acting as she does accordingto definite and invariable laws, can be rightly called an unintelligentagent, such a position as this is wholly untenable. Mix salt and sand, and it shall puzzle the wisest of men, with his mere natural appliances, to separate all the grains of sand from all the grains of salt; but ashower of rain will effect the same object in ten minutes. And so, whileman may find it tax all his intelligence to separate any variety whicharises, and to breed selectively from it, the destructive agenciesincessantly at work in Nature, if they find one variety to be moresoluble in circumstances than the other, will inevitably, in the longrun, eliminate it. 

A frequent and a just objection to the Lamarckian hypothesis of thetransmutation of species is based upon the absence of transitional formsbetween many species. But against the Darwinian hypothesis this argumenthas no force. Indeed, one of the most valuable and suggestive parts ofMr. Darwin's work is that in which he proves, that the frequent absenceof transitions is a necessary consequence of his doctrine, and thatthe stock whence two or more species have sprung, need in no respect beintermediate between these species. If any two species have arisen froma common stock in the same way as the carrier and the pouter, say, havearisen from the rock-pigeon, then the common stock of these two speciesneed be no more intermediate between the two than the rock-pigeon isbetween the carrier and pouter. Clearly appreciate the force ofthis analogy, and all the arguments against the origin of species byselection, based on the absence of transitional forms, fall to theground. And Mr. Darwin's position might, we think, have been evenstronger than it is if he had not embarrassed himself with the aphorism, "Natura non facit saltum, " which turns up so often in his pages. Webelieve, as we have said above, that Nature does make jumps now andthen, and a recognition of the fact is of no small importance indisposing of many minor objections to the doctrine of transmutation. 

But we must pause. The discussion of Mr. Darwin's arguments in detailwould lead us far beyond the limits within which we proposed, atstarting, to confine this article. Our object has been attained if wehave given an intelligible, however brief, account of the establishedfacts connected with species, and of the relation of the explanation ofthose facts offered by Mr. Darwin to the theoretical views held by hispredecessors and his contemporaries, and, above all, to the requirementsof scientific logic. We have ventured to point out that it does not, asyet, satisfy all those requirements; but we do not hesitate to assertthat it is as superior to any preceding or contemporary hypothesis, inthe extent of observational and experimental basis on which it rests, in its rigorously scientific method, and in its power of explainingbiological phenomena, as was the hypothesis of Copernicus to thespeculations of Ptolemy. But the planetary orbits turned out to benot quite circular after all, and, grand as was the service Copernicusrendered to science, Kepler and Newton had to come after him. What ifthe orbit of Darwinism should be a little too circular? What if speciesshould offer residual phenomena, here and there, not explicable bynatural selection? Twenty years hence naturalists may be in a positionto say whether this is, or is not, the case; but in either event theywill owe the author of 'The Origin of Species' an immense debt ofgratitude. We should leave a very wrong impression on the reader'smind if we permitted him to suppose that the value of that work dependswholly on the ultimate justification of the theoretical views which itcontains. On the contrary, if they were disproved to-morrow, the bookwould still be the best of its kind--the most compendious statementof well-sifted facts bearing on the doctrine of species that has everappeared. The chapters on Variation, on the Struggle for Existence, onInstinct, on Hybridism, on the Imperfection of the Geological Record, onGeographical Distribution, have not only no equals, but, so far asour knowledge goes, no competitors, within the range of biologicalliterature. And viewed as a whole, we do not believe that, since thepublication of Von Baer's Researches on Development, thirty years ago, any work has appeared calculated to exert so large an influence, notonly on the future of Biology, but in extending the domination ofScience over regions of thought into which she has, as yet, hardlypenetrated. 

[Footnote 1: 'The Westminster Review', April 1860. ]

[Footnote 2: On the Osteology of the Chimpanzees and Orangs:Transactions of the Zoological Society, 1858. ]

[Footnote 3: Colonel Humphreys' statements are exceedingly expliciton this point:--"When an Ancon ewe is impregnated by a common ram, theincrease resembles wholly either the ewe or the ram. The increase of thecommon ewe impregnated by an Ancon ram follows entirely the one orthe other, without blending any of the distinguishing and essentialpeculiarities of both. Frequent instances have happened where commonewes have had twins by Ancon rams, when one exhibited the complete marksand features of the ewe, the other of the ram. The contrast has beenrendered singularly striking, when one short-legged and one long-leggedlamb, produced at a birth, have been seen sucking the dam at the sametime. "--'Philosophical Transactions', 1813, Pt. I. Pp. 89, 90. ]

[Footnote 4: Recent investigations tend to show that this statement isnot strictly accurate. --1870. ]

[Footnote 5: See 'Phil. Zoologique, ' vol. I. P. 222, 'et seq. ']