_NATURE SERIES_ ARE THE EFFECTS OF USE AND DISUSE INHERITED? _AN EXAMINATION OF THE VIEW HELD BY SPENCER AND DARWIN_ BY WILLIAM PLATT BALL LONDON MACMILLAN AND CO. AND NEW YORK 1890 _The Right of Translation and Reproduction is Reserved_ RICHARD CLAY AND SONS, LIMITED, LONDON AND BUNGAY. PREFACE. My warmest thanks are due to Mr. Francis Darwin, to Mr. E. B. Poulton(whose interest in the subject here discussed is shown by his share inthe translation of Weismann's _Essays on Heredity_), and to ProfessorRomanes, for the help afforded by their kindly suggestions andcriticisms, and for the advice and recommendation under which this essayis now published. Encouragement from Mr. Francis Darwin is to me themore precious, and the more worthy of grateful recognition, from thefact that my general conclusion that acquired characters are _not_inherited is at variance with the opinion of his revered father, whoaided his great theory by the retention of some remains of Lamarck'sdoctrine of the inherited effect of habit. I feel as if the son, asrepresentative of his great progenitor, were carrying out the idea of anappreciative editor who writes to me: "We must say that if Darwin werestill alive, he would find your arguments of great weight, andundoubtedly would give to them the serious consideration which theydeserve. " I hope, then, that I may be acquitted of undue presumption inopposing a view sanctioned by the author of the _Origin of Species_, butalready stoutly questioned and firmly rejected by such followers of hisas Weismann, Wallace, Poulton, Ray Lankester, and others, to say nothingof its practical rejection by so great an authority on heredity asFrancis Galton. The sociological importance of the subject has already been insisted onin emphatic terms by Mr. Herbert Spencer, and this importance may beeven greater than he imagined. Civilization largely sets aside the harsh but ultimately salutary actionof the great law of Natural Selection without providing an efficientsubstitute for preventing degeneracy. The substitute on which moralistsand legislators rely--if they think on the matter at all--is thecumulative inheritance of the beneficial effects of education, training, habits, institutions, and so forth--the inheritance, in short, ofacquired characters, or of the effects of use and disuse. If thissubstitute is but a broken reed, then the deeper thinkers who graduallyteach the teachers of the people, and ultimately even influence thelegislators and moralists, must found their systems of morality andtheir criticisms of social and political laws and institutions andcustoms and ideas on the basis of the Darwinian law rather than on thatof Lamarck. Looking forward to the hope that the human race may become consciouslyand increasingly master of itself and of its destiny, and recognizingthe Darwinian principle of the selection of the fittest as the _only_means of preventing the moral and physical degeneracy which, like aninternal dry rot, has hitherto been the besetting danger of allcivilizations, I desire that the thinkers who mould the opinions ofmankind shall not be led astray from the true path of enduring progressand happiness by reliance on fallacious beliefs which will not bearexamination. Such, at least, is the feeling or motive which has promptedme to devote much time and thought to a difficult but important inquiryin a debatable region of inference and conjecture, where (I am afraid)evidence on either side can never be absolutely conclusive, and where, especially, the absolute demonstration of a universal negative cannotreasonably be expected. CONTENTS. PAGE PREFACE v IMPORTANCE AND BEARING OF THE INQUIRY 1 SPENCER'S EXAMPLES AND ARGUMENTS 6-44 DIMINUTION OF THE JAWS 6 DIMINISHED BITING MUSCLES OF LAP-DOGS 12 CROWDED TEETH 14 BLIND CAVE-CRABS 17 NO CONCOMITANT VARIATION FROM CONCOMITANT DISUSE 17 THE GIRAFFE, AND NECESSITY FOR CONCOMITANT VARIATION 18 ALLEGED RUINOUS EFFECTS OF NATURAL SELECTION 23 ADVERSE CASE OF NEUTER INSECTS 24 ÆSTHETIC FACULTIES 29 LACK OF EVIDENCE 34 INHERITED EPILEPSY IN GUINEA-PIGS 35 INHERITED INSANITY AND NERVOUS DISORDERS 36 INDIVIDUAL AND TRANSMISSIBLE TYPE NOT MODIFIED ALIKE 40 DARWIN'S EXAMPLES 45-100 REDUCED WINGS OF BIRDS OF OCEANIC ISLANDS 49 DROOPING EARS AND DETERIORATED INSTINCTS 53 WINGS AND LEGS OF DUCKS AND FOWLS 55 PIGEONS' WINGS 62 SHORTENED BREAST-BONE IN PIGEONS 64 SHORTENED FEET IN PIGEONS 70 SHORTENED LEGS OF RABBITS 70 BLIND CAVE-ANIMALS 72 INHERITED HABITS 73 TAMENESS OF RABBITS 76 MODIFICATIONS OBVIOUSLY ATTRIBUTABLE TO SELECTION 82 SIMILAR EFFECTS OF NATURAL SELECTION AND USE-INHERITANCE 83 INFERIORITY OF SENSES IN EUROPEANS 85 SHORT-SIGHT IN WATCHMAKERS AND ENGRAVERS 85 LARGER HANDS OF LABOURERS' INFANTS 87 THICKENED SOLE IN INFANTS 88 A SOURCE OF MENTAL CONFUSION 91 WEAKNESS OF USE-INHERITANCE 94 INHERITED INJURIES 101-118 INHERITED MUTILATIONS 101 THE MOTMOT'S TAIL 110 OTHER INHERITED INJURIES MENTIONED BY DARWIN 111 QUASI-INHERITANCE 116 MISCELLANEOUS CONSIDERATIONS 119-143 TRUE RELATION OF PARENTS AND OFFSPRING 119 INVERSE INHERITANCE 123 EARLY ORIGIN OF THE OVA 124 MARKED EFFECTS OF USE AND DISUSE ON THE INDIVIDUAL 126 WOULD NATURAL SELECTION FAVOUR USE-INHERITANCE? 127 USE-INHERITANCE AN EVIL 128 VARIED EFFECTS OF USE AND DISUSE 134 USE-INHERITANCE IMPLIES PANGENESIS 137 PANGENESIS IMPROBABLE 138 SPENCER'S EXPLANATION OF USE-INHERITANCE 141 CONCLUSIONS 144-156 USE-INHERITANCE DISCREDITED AS UNNECESSARY, UNPROVEN, AND IMPROBABLE 144 MODERN RELIANCE ON USE-INHERITANCE MISPLACED 145 ARE THE EFFECTS OF USE AND DISUSE INHERITED? IMPORTANCE AND BEARING OF THE INQUIRY. The question whether the effects of use and disuse are inherited, or, inother words, whether acquired characters are hereditary, is ofconsiderable interest to the general student of evolution; but it is, orshould be, a matter of far deeper interest to the thoughtfulphilanthropist who desires to ensure the permanent welfare and happinessof the human race. So profoundly important, in fact, are the moral, social, and political conclusions that depend on the answer to thisinquiry, that, as Mr. Herbert Spencer rightly says, it "demands, beyondall other questions whatsoever, the attention of scientific men. " It is obvious that we can produce important changes in the individual. We can, for example, improve his muscles by athletics, and his brain byeducation. The use of organs enlarges and strengthens them; the disuseof parts or faculties weakens them. And so great is the power of habitthat it is proverbially spoken of as "second nature. " It is thus certainthat we can modify the individual. We can strengthen (or weaken) hisbody; we can improve (or deteriorate) his intellect, his habits, hismorals. But there remains the still more important question which we areabout to consider. Will such modifications be inherited by the offspringof the modified individual? Does individual improvement transmit itselfto descendants independently of personal teaching and example? Haveartificially produced changes of structure or habit any inherenttendency to become congenitally transmissible and to be converted intime into fixed traits of constitution or character? Can thephilanthropist rely on such a tendency as a hopeful factor in theevolution of mankind?--the only sound and stable basis of a higher andhappier state of things being, as he knows or ought to know, the innateand constitutionally-fixed improvement of the race as a whole. Ifacquired modifications are impressed on the offspring and on the race, the systematic moral training of individuals will in time produce aconstitutionally moral race, and we may hope to improve mankind even indefiance of the unnatural selection by which a spurious but highlypopular philanthropy would systematically favour the survival of theunfittest and the rapid multiplication of the worst. But if acquiredmodifications do not tend to be transmitted, if the use or disuse oforgans or faculties does not similarly affect posterity by inheritance, then it is evident that no innate improvement in the race can take placewithout the aid of natural or artificial selection. Herbert Spencer maintains that the effects of use and disuse _are_inherited in kind, and in his _Factors of Organic Evolution_[1] he hassupported his contention with a selection of facts and reasonings whichI shall have the temerity to examine and criticize. Darwin also held thesame view, though not so strongly. And here, to preventmisunderstanding, I may say that the admiration and reverence andgratitude due to Darwin ought not to be allowed to interfere in theslightest degree with the freest criticism of his conclusions. Toperfect his work by the correction of really extraneous errors is asmuch a sacred duty as to study and apply the great truths he has taught. FOOTNOTES: [1] Which originally appeared in the _Nineteenth Century_ for April andMay, 1886. SPENCER'S EXAMPLES AND ARGUMENTS. DIMINUTION OF THE JAWS IN CIVILIZED RACES. Mr. Spencer verified this by comparing English jaws with Australian andNegro jaws at the College of Surgeons. [2] He maintains that thediminution of the jaw in civilized races can _only_ have been broughtabout by inheritance of the effects of lessened use. But if English jawsare lighter and thinner than those of Australians and Negroes, so too isthe rest of the skull. As the diminution in the weight and thickness ofthe walls of the cranium cannot well be ascribed to disuse, it must beattributed to some other cause; and this cause may have affected the jawalso. Cessation of the process by which natural selection[3] favouredstrong thick bones during ages of brutal violence might bring about achange in this direction. Lightness of structure, facilitating agilityand being economical of material, would also be favoured by naturalselection so far as strength was not too seriously diminished. Sexual selection powerfully affects the human face, and so must affectthe jaws--as is shown by the differences between male and female jaws, and by the relative lightness and smallness of the latter, especially inthe higher races. Human preference, both sexual and social, would tendto eliminate huge jaws and ferocious teeth when these were no longerneeded as weapons of war or organs of prehension, &c. We can hardlyassume that the lower half of the face is specially exempt from theinfluence of natural and sexual selection; and the effects of theseundoubted factors of evolution must be fully considered before we areentitled to call in the aid of a factor whose existence is questioned. After allowing for lost teeth and the consequent alveolar absorption, and for a reduction proportional to that shown in the rest of the skull, the difference in average weight in fifty European and fourteenAustralian male jaws at the College of Surgeons turned out to be lessthan a fifth of an ounce, or about 5 per cent. This slight reduction maybe much more than accounted for by such causes as disuse in theindividual, human preference setting back the teeth, and partialtransference of the much more marked diminution seen in female jaws. There is apparently no room for accumulated _inherited_ effects ofancestral disuse. The number of jaws is small, indeed; but weighing themis at least more decisive than Mr. Spencer's mere inspection. The differences between Anglo-Saxon male jaws and Australian andTasmanian jaws are most easily explained as effects of human preferenceand natural selection. We can hardly suppose that disuse would maintainor develop the projecting chin, increase its perpendicular height tillthe jaw is deepest and strongest at its extremity, evolve a side flange, and enlarge the upper jaw-bone to form part of a more prominent nose, while drawing back the savagely obtrusive teeth and lips to a morepleasing and subdued position of retirement and of humanized beauty. Ifhuman preference and natural selection caused some of these differences, why are they incompetent to effect changes in the direction of adiminution of the jaw or teeth? And if use and disuse are the solemodifying agents in the case of the human jaw, why should men have anymore chin than a gorilla or a dog? The excessive weight of the West African jaws at the College of Surgeonsis partly _against_ Mr. Spencer's contention, unless he assumes thatGuinea Negroes use their jaws far more than the Australians, asupposition which seems extremely improbable. The heavier skull andnarrower molar teeth point however to other factors than increased use. The striking variability of the human jaw is strongly opposed to theidea of its being under the direct and dominant control of so uniform acause as ancestral use and disuse. Mr. Spencer regards a variation of 1oz. As a large one, but I found that the English jaws in the College ofSurgeons varied from 1·9 oz. To 4·3 oz. (or 5 oz. If lost teeth wereallowed for); Australian jaws varied from 2 oz. To 4·5 oz. (with _no_lost teeth to allow for); while in Negro jaws the maximum rose to over5-1/2 oz. [4] In spite of disuse some European jaws were twice as heavyas the lightest Australian jaw, either absolutely or (in some cases)relatively to the cranium. The uniformity of change relied upon by Mr. Spencer is scarcely borne out by the facts so far as male jaws areconcerned. The great reduction in the weight of _female_ jaws _andskulls_ evidently points to sexual selection and to panmixia under maleprotection. I think, on the whole, we must conclude that the human jaws do notafford satisfactory proof of the inheritance of the effects of use anddisuse, inasmuch as the differences in their weight and shape and sizecan be more reasonably and consistently accounted for as the result ofless disputable causes. DIMINISHED BITING MUSCLES OF LAP-DOGS. The next example, the reduced biting muscles, &c. , of lap-dogs is alsounsatisfactory as a proof of the inheritance of the effects of disuse;for the change can readily be accounted for without the introduction ofsuch a factor. The previous natural selection of strong jaws and teethand muscles is reversed. The conscious or unconscious selection oflap-dogs with the least tendency to bite would easily bring about ageneral enfeeblement of the whole biting apparatus--weakness of theparts concerned favouring harmlessness. Mr. Spencer maintains that thedwindling of the parts concerned in clenching the jaw is certainly notdue to artificial selection because the modifications offer noappreciable external signs. Surely hard biting is sufficientlyappreciable by the person bitten without any visual admeasurement of themasseter muscles or the zygomatic arches. Disuse during lifetime wouldalso cause some amount of degeneracy; and I am not sure that Mr. Spenceris right in _entirely_ excluding economy of nutrition from the problem. Breeders would not over-feed these dogs; and the puppies that grew mostrapidly would usually be favoured. CROWDED TEETH. The too closely-packed teeth in the "decreasing" jaws of modern men (p. 13)[5] are also suggestive of other causes than use and disuse. Why isthere not simultaneous variation in teeth and jaws, if disuse is thegoverning factor? Are we to suppose that the size of the human teeth ismaintained by use at the same time that the jaws are being diminished bydisuse? Mr. Spencer acknowledges that the crowding of bull-dogs' andlap-dogs' teeth is caused by the artificial selection of shortened jaws. If a similar change is really occurring in man, could it not besimilarly explained by some factor, such as sexual selection, whichmight affect the outward appearance at the cost of less obvious defectsor inconveniences? Mr. Spencer points to the decay of modern teeth as a sign or result oftheir being overcrowded through the diminution of the jaw by disuse. [6]But the teeth which are the most frequently overcrowded are the lowerincisors. The upper incisors are less overcrowded, being commonlypressed outwards by the lower arc of teeth fitting inside them inbiting. The lower incisors are correspondingly pressed inwards andcloser together. Yet the upper incisors decay--or at least areextracted--about twenty times as frequently as the closely packed lowerincisors. [7] Surely this must indicate that the cause of decay is notovercrowding. The lateness and irregularity of the wisdom teeth are sometimessupposed to indicate their gradual disappearance through want of room ina diminishing jaw. But a note on Tasmanian skulls in the _Catalogue ofthe College of Surgeons_ (p. 199) shows that this lateness andirregularity have been common among Tasmanians as well as amongcivilized races, so that the change can hardly be attributed to theeffects of disuse under civilization. BLIND CAVE-CRABS. The cave-crabs which have lost their disused eyes but _not the disusedeye-stalks_ appear to illustrate the effects of natural selection ratherthan of disuse. The loss of the exposed, sensitive, andworse-than-useless eye, would be a decided gain, while the disusedeye-stalk, being no particular detriment to the crab, would be butslightly affected by natural selection, though open to the cumulativeeffects of disuse. The disused but better protected eyes of the blindcave-rat are still "of large size" (_Origin of Species_, p. 110). NO CONCOMITANT VARIATION FROM CONCOMITANT DISUSE. It is but fair to add that these instances of the cave-crab's eye-stalkand the closely-packed teeth are put forward by Mr. Spencer with themore immediate object of proving that there is "no concomitantvariation in co-operative parts, " even when "formed out of the sametissue, like the crab's eye and its peduncle" (pp. 12-14, 23, 33). Itescapes his notice, however, that in two out of his three cases it is_disuse_, or _diminished use_, which fails to cause concomitantvariation or proportionate variation. THE GIRAFFE, AND NECESSITY FOR CONCOMITANT VARIATION. Having unwittingly shown that lessened use of closely-connected andco-operative parts does not cause concomitant variation in these parts, Mr. Spencer concludes that the concomitant variation requisite forevolution can only be caused by altered degrees of use or disuse. Heelaborately argues that the many co-ordinated modifications of partsnecessitated by each important alteration in an animal are so complexthat they cannot possibly be brought about except by the inheritedeffect of the use and disuse of the various parts concerned. He holds, for instance, that natural selection is inadequate to effect thenumerous concomitant changes necessitated by such developments as thatof the long neck of the giraffe. Darwin, however, on the contrary, holdsthat natural selection alone "would have sufficed for the production ofthis remarkable quadruped. "[8] He is surprised at Mr. Spencer's viewthat natural selection can do so little in modifying the higher animals. Thus one of the chief arguments with which Mr. Spencer supports histheory is so poorly founded as to be rejected by a far greater authorityon such subjects. All that is needed is that natural selection shouldpreserve the tallest giraffes through times of famine by their beingable to reach otherwise inaccessible stores of foliage. The continualvariability of all parts of the higher animals gives scope forinnumerable changes, and Nature is not in a hurry. Mr. Spencer, however, says that "the chances against any adequate readjustments fortuitouslyarising must be infinity to one. " But he has also shown that altereddegree of use does not cause the needed concomitant variation ofco-operative parts. So the chances against a beneficial change in ananimal must be, at a liberal estimate, infinity to two. Mr. Spencer, ifhe has proved anything, has proved that it is practically impossiblethat the giraffe can have acquired a long neck, or the elk its hugehorns, or that any species has ever acquired any important modification. Mr. Wallace, in his _Darwinism_, answers Mr. Spencer by a collection offacts showing that "variation is the rule, " that the range of variationin wild animals and plants is much greater than was supposed, and that"each part varies to a considerable extent independently" of otherparts, so that "the materials constantly ready for natural selection toact upon are abundant in quantity and very varied in kind. " Whileco-operative parts would often be more or less correlated, so that theywould tend to vary together, coincident variation is not necessary. Thelengthened wing might be gained in one generation, and the strengthenedmuscle at a subsequent period; the bird in the meanwhile drawing uponits surplus energy, aided (as I would suggest) by the strengtheningeffect of increased use in the individual. Seeing that artificialselection of complicated variations has modified animals in many pointseither simultaneously or by slow steps, as with otter-sheep, fancypigeons, &c. (many of the characters thus obtained being clearlyindependent of use and disuse), natural selection must be credited withsimilar powers, and Mr. Wallace concludes that Mr. Spencer'sinsuperable difficulty is "wholly imaginary. " The extract concerning a somewhat similar "class of difficulties, " whichMr. Spencer quotes from his _Principles of Biology_, is faulty in itsreasoning, [9] though legitimate in its conclusion concerning theincreasing difficulty of evolution in proportion with the increasingnumber and complexity of faculties to be evolved. But this increasingdifficulty of complex evolution is only overcome by _some_favourably-varying individuals and species--not by all. And as thedifficulty increases we find neglect and decay of the less-neededfaculties--as with domesticated animals and civilized men, who lose inone direction while they gain in another. The increasing difficulty ofcomplex evolution by natural selection is no proof whatever ofuse-inheritance[10] except to those who confound difficulty withimpossibility. ALLEGED RUINOUS EFFECTS OF NATURAL SELECTION. Mr. Spencer further contends that natural selection, by undulydeveloping specially advantageous modifications without the necessarybut complex secondary modifications, would render the constitution of avariety "unworkable" (p. 23). But this seems hardly feasible, seeingthat natural selection must continually favour the most workableconstitutions, and will only preserve organisms in proportion as theycombine general workableness with the special modification. On the otherhand, according to Mr. Spencer himself, use-inheritance must oftendisturb the balance of the constitution. Thus it tends to make the jawsand teeth unworkable through the overcrowding and decay of theteeth--there being, as his illustrations show, no simultaneous orconcomitant or proportional variation in relation to altered degree ofuse or disuse. ADVERSE CASE OF NEUTER INSECTS. Mr. Spencer also holds that most mental phenomena, especially wherecomplex or social or moral, can only be explained as arising fromuse-inheritance, which becomes more and more important as a factor ofevolution as we advance from the vegetable world and the lower grades ofanimal life to the more complex activities, tastes, and habits of thehigher organizations (preface, and p. 74). But there happens to be atolerably clear proof that such changes as the evolution of complicatedstructures and habits and social instincts _can_ take placeindependently of use-inheritance. The wonderful instincts of the workingbees have apparently been evolved (at least in all their later socialcomplications and developments) without the aid of use-inheritance--nay, in spite of its utmost opposition. Working bees, being infertile"neuters, " cannot as a rule transmit their own modifications and habits. They are descended from countless generations of queen bees and drones, whose habits have been widely different from those of the workers, andwhose structures are dissimilar in various respects. In many species ofants there are two, and in the leaf-cutting ants of Brazil there are_three_, kinds of neuters which differ from each other and from theirmale and female ancestors "to an almost incredible degree. "[11] Thesoldier caste is distinguished from the workers by enormously largeheads, very powerful mandibles, and "extraordinarily different"instincts. In the driver ant of West Africa one kind of neuter is threetimes the size of the other, and has jaws nearly five times as long. Inanother case "the workers of one caste alone carry a wonderful sort ofshield on their heads. " One of the three neuter classes in theleaf-cutting ants has a single eye in the midst of its forehead. Incertain Mexican and Australian ants some of the neuters have hugespherical abdomens, which serve as living reservoirs of honey for theuse of the community. In the equally wonderful case of the termites, orso-called "white ants" (which belong, however, to an entirely differentorder of insect from the ants and bees) the neuters are blind andwingless, and are divided into soldiers and workers, each classpossessing the requisite instincts and structures adapting it for itstasks. Seeing that natural selection can form and maintain the variousstructures and the exceedingly complicated instincts of ants and beesand wasps and termites in direct defiance of the alleged tendency touse-inheritance, surely we may believe that natural selection, unopposed by use-inheritance, is equally competent for the work ofcomplex or social or mental evolution in the many cases where the strongpresumptive evidence cannot be rendered almost indisputable by theexceptional exclusion of the modified animal from the work ofreproduction. Ants and bees seem to be capable of altering their habits and methods ofaction much as men do. Bees taken to Australia cease to store honeyafter a few years' experience of the mild winters. Whole communities ofbees sometimes take to theft, and live by plundering hives, firstkilling the queen to create dismay among the workers. Slave ants attenddevotedly to their captors, and fight against their own species. Forelreared an artificial ant-colony made up of five different and more orless hostile species. Why cannot a much more intelligent animal modifyhis habits far more rapidly and comprehensively without the aid of afactor which is clearly unnecessary in the case of the more intelligentof the social insects? ÆSTHETIC FACULTIES. The modern development of music and harmony (p. 19) is undeniable, butwhy could it only have been brought about by the help of the inheritanceof the effects of use? Why are we to suppose that "minor traits" such asthe "æsthetic perceptions" cannot have been evolved by natural selection(p. 20) or by sexual selection? Darwin holds that our musical facultieswere developed by sexual preference long before the acquisition ofspeech. He believes that the "rhythms and cadences of oratory arederived from previously developed musical powers"--a conclusion "exactlyopposite" to that arrived at by Mr. Spencer. [12] The emotionalsusceptibility to music, and the delicate perceptions needed for thehigher branches of art, were apparently the work of natural and sexualselection in the long past. Civilization, with its leisure and wealthand accumulated knowledge, perfects human faculties by artificialcultivation, develops and combines means of enjoyment, and discoversunsuspected sources of interest and pleasure. The sense of harmony, modern as it seems to be, must have been a latent and indirectconsequence of the development of the sense of hearing and of melody. Use, at least, could never have called it into existence. Nature favoursand develops enjoyments to a certain extent, for they subserveself-preservation and sexual and social preference in innumerable ways. But modern æsthetic advance seems to be almost entirely due to theculture of latent abilities, the formation of complex associations, theselection and encouragement of talent, and the wide diffusion andimitation of the accumulated products of the well-cultivated genius offavourably varying individuals. The fact that uneducated persons do notenjoy the higher tastes, and the rapidity with which such tastes areacquired or professed, ought to be sufficient proof that modern cultureis brought about by far swifter and more potent influences thanuse-inheritance. Neither would this hypothetical factor of evolutionmaterially aid in explaining the many other rapid changes of habitbrought about by education, custom, and the changed conditions ofcivilization generally. Powerful tastes--as is incontestably shown inthe cases of alcohol and tobacco--lie latent for ages, and suddenlybecome manifest when suitable conditions arise. Every discovery, andeach step in social and moral evolution, produces its wide-spreadingtrain of consequences. I see no reason why use-inheritance need becredited with any share in the cumulative results of the invention ofprinting and the steam-engine and gunpowder, or of freedom and securityunder representative government, or of science and art and the partialemancipation of the mind of man from superstition, or of the innumerableother improvements or changes that take place under modern civilization. Mr. Spencer suggests an inquiry whether the greater powers possessed byeminent musicians were not mainly due to the inherited effect of themusical practice of their fathers (p. 19). But these great musiciansinherited far more than their parents possessed. The excess of theirpowers beyond their parents' must surely be attributed to spontaneousvariation; and who shall say that the rest was in any way due touse-inheritance? If, too, the superiority of geniuses provesuse-inheritance, why should not the inferiority of the sons of geniusesprove the existence of a tendency which is the exact opposite ofuse-inheritance? But nobody collects facts concerning the degeneratebranches of musical families. Only the favourably varying branches arenoticed, and a general impression of rapid evolution of talent is thusproduced. Such cases might be explained, too, by the facts that musicalfaculty is strong in both sexes, that musical families associatetogether, and that the more gifted members may intermarry. Greatmusicians are often astonishingly precocious. Meyerbeer "playedbrilliantly" at the age of six. Mozart played beautifully at four. Arewe to suppose that the effect of the _adult_ practice of parents wasinherited at this early age? If use-inheritance was not necessary in thecase of Handel, whose father was a surgeon, why is it needed to accountfor Bach? LACK OF EVIDENCE. The "direct proofs" of use-inheritance are not as plentiful as might bedesired, it appears (pp. 24-28). This acknowledged "lack of recognizedevidence" is indeed the weakest feature in the case, though Mr. Spencerwould fain attribute this lack of direct proof to insufficientinvestigation and to the inconspicuous nature of the inheritance of themodification. But there is an almost endless abundance of conspicuousexamples of the effects of use and disuse in the individual. How is itthat the subsequent inheritance of these effects has not been moresatisfactorily observed and investigated? Horse-breeders and otherscould profit by such a tendency, and one cannot help suspecting that thereason they ignore it must be its practical inefficacy, arising probablyfrom its weakness, its obscurity and uncertainty or its non-existence. INHERITED EPILEPSY IN GUINEA-PIGS. Brown-Séquard's discovery that an epileptic tendency artificiallyproduced by mutilating the nervous system of a guinea-pig isoccasionally inherited may be a fact of "considerable weight, " or on theother hand it may be entirely irrelevant. Cases of this kind strike oneas peculiar exceptions rather than as examples of a general rule or law. They seem to show that certain morbid conditions may occasionally affectboth the individual and the reproductive elements or transmissible typein a similar manner; but then we also know that such prompt and completetransmission of an artificial modification is widely different from theusual rule. Exceptional cases require exceptional explanations, and arescarcely good examples of the effect of a general tendency which inalmost all other cases is so inconspicuous in its immediate effects. Further remarks on this inherited epilepsy can be most convenientlyintroduced later on in connection with Darwin's explanation of theinherited mutilation which it usually accompanies, but which Mr. Spencerdoes not mention. INHERITED INSANITY AND NERVOUS DISORDERS. Mr. Spencer infers that, because insanity is usually hereditary, andinsanity can be artificially produced by various excesses, thereforethis artificially-produced insanity must also be hereditary (p. 28). Direct evidence of this conclusion would be better than a mere inferencewhich may beg the very question at issue. That the liability to insanitycommonly runs in families is no proof that strictly non-inheritedinsanity will subsequently become hereditary. I think that theoriesshould be based on facts rather than facts on theories, especially whenthose facts are to be the basis or proof of a further theory. Mr. Spencer also points out that he finds among physicians "the beliefthat nervous disorders of a less severe kind are inheritable"--a generalbelief which does not necessarily include the transmission of purelyartificially-produced disorders, and so misses the point which is reallyat issue. He proceeds, however, to state more definitely that "men whohave prostrated their nervous systems by prolonged overwork or in someother way, have children more or less prone to nervousness. " Thefollowing observations will, I think, warrant at least a suspension ofjudgment concerning this particular form of use-inheritance. (1) The nervousness is seen in the _children_ at an early age, althoughthe nervous prostration from which it is supposed to be derivedobviously occurs in the parent at a much later period of life. Thischange in time is contrary to the rule of inheritance at correspondingperiods; and, together with the unusual promptness and comparativecompleteness of the inheritance, it may indicate a special injury ordeterioration of the reproductive elements rather than true inheritance. The healthy brain of early life has failed to transmit its robustcondition. Is use-inheritance, then, only effective for evil? Does itonly transfer the newly-acquired weakness, and not the previouslong-continued vigour? (2) Members of nervous families would be liable to suffer from nervousprostration, and by the ordinary law of heredity alone would transmitnervousness to their children. (3) The shattered nerves or insanity resulting from alcoholic and otherexcesses, or from overwork or trouble, are evidently signs of a graveconstitutional injury which may react upon the reproductive elementsnourished and developed in that ruined constitution. The deteriorationin parent and child may often display itself in the same organs--thoseprobably which are hereditarily weakest. Acquired diseases or disordersthus appear to be transmitted, when all that was conveyed to theoffspring was the exciting cause of a lowered vitality or disorderedaction, together with the ancestral liability to such diseases undersuch conditions. (4) Francis Galton says that "it is hard to find evidence of the powerof the personal structure to react upon the sexual elements, that is notopen to serious objection. " Some of the cases of apparent inheritance heregards as coincidence of effect. Thus "the fact that a drunkard willoften have imbecile children, although his offspring previous to histaking to drink were healthy, " is an "instance of simultaneous action, "and not of true inheritance. "The alcohol pervades his tissues, and, ofcourse, affects the germinal matter in the sexual elements as much as itdoes that in his own structural cells, which have led to an alterationin the quality of his own nerves. Exactly the same must occur in thecase of many constitutional diseases that have been acquired bylong-continued irregular habits. "[13] INDIVIDUAL AND TRANSMISSIBLE TYPE NOT MODIFIED ALIKE BY THE DIRECTEFFECT OF CHANGED HABITS OR CONDITIONS. Mr. Spencer finds it hard to believe that the modifications conveyed tooffspring are not identical in tendency with the changes effected in theparent by altered use or habit (pp. 23-25, 34). But it is perfectlycertain that the two sets of effects do not necessarily correspond. Theeffect of changed habits or conditions on the individual is often veryfar from coinciding with the effects on the reproductive elements orthe transmissible type. The reproductive system is "extremelysensitive" to very slight changes, and is often powerfully affected bycircumstances which otherwise have little effect on the individual(_Origin of Species_, p. 7). Various animals and plants become sterilewhen domesticated or supplied with too much nourishment. The nativeTasmanians have already become extinct from sterility caused by greatlychanged diet and habits. If, as Mr. Spencer teaches, continued cultureand brain-work will in time produce lessened fertility or comparativesterility, we may yet have to be careful that intellectual developmentdoes not become a species of suicide, and that the culture of the racedoes not mean its extinction--or at least the extinction of those mostsusceptible of culture. The reproductive elements are also disturbed and modified in innumerableminor ways. Changed conditions or habits tend to produce a general"plasticity" of type, the "indefinite variability" thus caused beingapparently irrelevant to the change, if any, in the individual. [14] Avast number of variations of structure have certainly arisenindependently of similar parental modification as the preliminary. Whatever first caused these "spontaneous" congenital variations affectedthe reproductive elements quite differently from the individual. "When anew peculiarity first appears we can never predict whether it will beinherited. " Many varieties of plants only keep true from shoots, and notfrom seed, which is by no means acted on in the same way as theindividual plant. Seeing that such plants have _two_ reproductivetypes, both constant, it is evident that these cannot both be modifiedin the same way as the parent is modified. Many parental modificationsof structure and habit are certainly not conveyed to neuter ants andbees; other modifications, which are not seen in the parents, beingconveyed instead. Many other circumstances tend to show that theindividual and the transmissible type are independent of each other sofar as modifications of parts are concerned. It may seem natural to expect the transmission of an enlarged muscle ora cultivated brain, but, on the other hand, why should it beunreasonable to expect that a modification which was non-congenital inorigin should still remain non-congenital? Why should thenon-transmission of that which was not transmitted be surprising? Mr. Spencer thinks that the non-transmission of acquired modificationsis incongruous with the great fact of atavism. But the great law of theinheritance of that which is a development of the transmissible typedoes not necessarily imply the inheritance of modifications acquired bythe individual. Because English children may inherit blue eyes andflaxen hair from their Anglo-Saxon ancestors, it by no means followsthat an Englishman must inherit his father's sunburnt complexion orsmooth-shaven face. Of course atavism ultimately adopts many instancesof revolt against its sway. But to assume that these changes of type_follow_ the personal change rather than cause it, is to assume thewhole question at issue. That like begets like is true as a broadprinciple, but it has many exceptions, and the non-heredity of acquiredcharacters may be one of them. FOOTNOTES: [2] _Principles of Biology_, § 166, footnote. The English jaws aresomewhat lighter than the Australian jaws, though I could not undertaketo affirm that they are really shorter and smaller. In the typicalskulls depicted on p. 68 of the official guide to the mammaliangalleries at South Kensington, the typical Caucasian jaw is very muchlarger than the Tasmanian jaw, although the repulsively obtrusive teethof the latter convey the contrary idea to the imagination. Mr. Spencer'sassumption that the ancient Britons had large jaws appears to meerroneous. (See Professor Rolleston's _Scientific Papers and Addresses_, i. P. 250. ) [3] Romanes, Galton, and Weismann have made great use of this principlein explaining the diminution of disused organs. Weismann has given itthe name of _Panmixia_, --_all_ individuals being equally free to surviveand commingle their variations, and not merely selected or favouredindividuals. See his _Essays on Heredity_, &c. , p. 90 (Clarendon Press). [4] Inclusive in each case of fixed strengthening wire weighing about asixteenth of an ounce or less. [5] References of course are to _Factors of Organic Evolution_. [6] P. 13; and _Nineteenth Century_, February, 1888, p. 211. [7] Tomes's _Dental Surgery_, pp. 273-275. Tomes observes that it is asyet uncertain in what way civilization predisposes to caries. But heshows that caries is caused by the lime salts in the teeth beingattacked by _acids_ from decomposing food in crevices, from artificialdrink such as cyder, from sugar, from medicine, and from vitiatedsecretions of the mouth. It is evident that in civilized races naturalselection cannot so rigorously insist on sound teeth, soundconstitutions, and _protective alkaline_ saliva. The reaction of thecivilized mouth is often acid, especially when the system is disorderedby dyspepsia or other diseases or forms of ill-health common undercivilization. The main supply of saliva, which is poured from the cheeksopposite the upper molars, is often acid when in small quantities. Butthe submaxillary and sub-lingual saliva poured out at the foot of thelower incisors and held in the front part of the jaw as in a spoon, "differs from parotid saliva in being more alkaline" (Foster's _TextBook of Physiology_, p. 238; Tomes, pp. 284, 685). One observer saysthat the reaction near the lower incisors is "never acid. " Hence (Iconclude) the remarkable immunity of the lower incisors and canines fromdecay, an immunity which extends backwards in a lessening degree to thefirst and second bicuspids. The close packing of the lower incisors mayassist by preventing the retention of decaying fragments of food. Sexualselection may promote caries by favouring white teeth, which are moreprone to decay than yellow ones. Acid vitiation of the mucus mightaccount both for caries and (possibly) for the strange infertility ofsome inferior races under civilization. [8] _Origin of Species_, pp. 198-9; _Variation of Animals and Plantsunder Domestication_, vol. Ii. P. 328 footnote, also p. 206. [9] Mr. Spencer weakly argues that an advantageous attribute (such asswiftness, keen sight, courage, sagacity, strength, &c. ) cannot beincreased by natural selection unless it is "of greater importance, forthe time being, than most of the other attributes"; and that naturalselection cannot develop any one superiority when animals are equallypreserved by "other superiorities. " But as natural selection willsimultaneously eliminate tendencies to slowness, blindness, deafness, stupidity, &c. , it _must_ favour and improve many points simultaneously, although no one of them may be of greater importance than the rest. Ofcourse the more complicated the evolution the slower it will be; buttime is plentiful, and the amount of elimination is correspondinglyvast. [10] I venture to coin this concise term to signify _the directinheritance of the effects of use and disuse in kind_. Having a name fora thing is highly convenient; it facilitates clearness and accuracy inreasoning, and in this particular inquiry it may save some confusion ofthought from double or incomplete meanings in the shortened phraseswhich would otherwise have to be employed to indicate this great butnameless factor of evolution. [11] _Origin of Species_, pp. 230-232; Bates's _Naturalist on theAmazons_. Darwin is "surprised that no one has hitherto advanced thedemonstrative case of neuter insects, against the well-known doctrine ofinherited habit, as advanced by Lamarck. " As he justly observes, "itproves that with animals, as with plants, any amount of modification maybe effected by the accumulation of numerous, slight, spontaneousvariations, which are in any way profitable, without exercise or habithaving been brought into play. For peculiar habits confined to theworkers or sterile females, however long they might be followed, couldnot possibly affect the males and fertile females, which alone leave anydescendants. " Some slight modification of these remarks, however, maypossibly be needed to meet the case of "factitious queens, " who(probably through eating particles of the royal food) become capable ofproducing a few male eggs. [12] _Descent of Man_, pp. 573, 572, and footnote. [13] _Contemporary Review_, December, 1875, p. 92. [14] See _Origin of Species_, pp. 5-8. "Changed conditions induce analmost indefinite amount of fluctuating variability, by which the wholeorganization is rendered in some degree plastic" (_Descent of Man_, p. 30). It also appears that "the nature of the conditions is ofsubordinate importance in comparison with the nature of the organism indetermining each particular form of variation;--perhaps of not moreimportance than the nature of the spark, by which a mass of combustiblematter is ignited, has in determining the nature of the flames" (_Originof Species_, p. 8). DARWIN'S EXAMPLES. The most formidable cases brought forward by Mr. Spencer are fromDarwin. I shall endeavour to show, however, that Darwin was probablywrong in retaining the older explanation of these facts, and that theremains of the Lamarckian theory of use-inheritance need not any longerencumber the great explanation which has superseded that fallacious andunproven theory and has rendered it totally unnecessary. Meanwhile Ithink it is an excellent sign that Mr. Spencer has to complain that"Nowadays most naturalists are more Darwinian than Mr. Darwinhimself"--inasmuch as they are inclined to say that there is "no proof"that the effects of use and disuse are inherited. Other excellent signsare the recent issue of a translation of Weismann's important essays onthis and kindred subjects, [15] the strong support given to his views byWallace in his _Darwinism_, and their adoption by Ray Lankester in hisarticle on Zoology in the latest edition of the _EncyclopædiaBritannica_. So sound and cautious an investigator as Francis Galton hadalso in 1875 concluded that "acquired modifications are barely, if atall, _inherited_, in the correct sense of that word. " Darwin's belief in the inheritance of acquired characters was more orless hereditary in the family. His grandfather, Erasmus Darwin, anticipated Lamarck's views in his _Zoonomia_, which Darwin at one time"greatly admired. " His father was "convinced" of the "inherited evileffects of alcohol, " and to this extent at least he strongly impressedthe belief in the inheritance of acquired characters upon hischildren's minds. [16] Darwin must also have been imbued with Lamarckianideas from other sources, although Dr. Grant's enthusiastic advocacyentirely failed to convert him to a belief in evolution. [17]"Nevertheless, " he says, "it is probable that the hearing rather earlyin life such views maintained and praised may have favoured my upholdingthem under a different form in my _Origin of Species_"--a remark whichrefers to Lamarck's views on the general doctrine of evolution, butmight also prove equally true if applied to Darwin's partial retentionof the Lamarckian explanation of that evolution. Professor Huxley haspointed out that in Darwin's earlier sketch of his theory of evolution(1844) he attached more weight to the inheritance of acquired habitsthan he does in his _Origin of Species_ published fifteen yearslater. [18] He appears to have acquired the belief in early life withoutfirst questioning and rigorously testing it as he would have done had itoriginated with himself. In later life it appeared to assist his theoryof evolution in minor points, and in particular it appeared absolutelyindispensable to him as the _only_ explanation of the diminution ofdisused parts in cases where, as in domestic animals, economy of growthseemed to be practically powerless. He failed to adequately notice theeffect of panmixia, or the withdrawal of selection, in causing orallowing degeneracy and dwindling under disuse; and he hardly attachedsufficient importance to the fact that rudimentary organs and othersupposed effects of use or disuse are quite as marked features inneuter insects which cannot transmit the effects of use and disuse asthey are in the higher animals. REDUCED WINGS OF BIRDS OF OCEANIC ISLANDS. Darwin himself has pointed out that the rudimentary wings of islandbeetles, at first thought to be due to disuse, are mainly brought aboutby natural selection--the best-winged beetles being most liable to beblown out to sea. But he says that in birds of the oceanic islands "notpersecuted by any enemies, the reduction of their wings has probablybeen caused by disuse. " This explanation may be as fallacious as it isacknowledged to have been in the case of the island beetles. Accordingto Darwin's own views, natural selection _must_ at least have played animportant part in reducing the wings; for he holds that "naturalselection is continually trying to economize every part of theorganization. " He says: "If under changed conditions of life astructure, before useful, becomes less useful, its diminution will befavoured, for it will profit the individual not to have its nutrimentwasted in building up an useless structure. .. . Thus, as I believe, natural selection will tend in the long run to reduce any part of theorganization, as soon as it becomes, through changed habits, superfluous. "[19] If, as Darwin powerfully urges (and he here ignoreshis usual explanation), ostriches' wings are insufficient for flight inconsequence of the economy enforced by natural selection, [20] why maynot the reduced wings of the dodo, or the penguin, or the apteryx, or ofthe Cursores generally, be wholly attributed to natural selection infavour of economy of material and adaptation of parts to changedconditions? The great principle of economy is continually at workshaping organisms, as sculptors shape statues, by removing thesuperfluous parts; and a mere glance at the forms of animals in generalwill show that it is well-nigh as dominant and universal a principle asis that of the positive development of useful parts. Other causes, moreover besides actual economy, would favour shorter and moreconvenient wings on oceanic islands. In the first place, birds that weresomewhat weak on the wing would be most likely to settle on an islandand stay there. Shortened wings would then become advantageous becausethey would restrain fatal migratory tendencies or useless and perilousflights in which the birds that flew furthest would be most oftencarried away by storms and adverse winds. Reduced wings would keep thebirds near the shelter and the food afforded by the island and itsneighbourhood, and in some cases would become adapted to act as fins orflappers for swimming under water in pursuit of fish. The reduced size of the wings of these island birds is paralleled by theremarkable thinness, &c. , of the shell of the "gigantic land-tortoise"of the Galapagos Islands. The changes seen in the carapace can hardlyhave been brought about by the inherited effects of special disuse. Whythen should not the reduction of equally useless, more wasteful, andperhaps positively dangerous wings be also due to an economy which hasbecome advantageous to bird and reptile alike through the absence of themammalian rivals whose places they are evidently being modified to fill?The _complete_ loss of the wings in neuter ants and termites canscarcely be due to the inherited effects of disuse; and as naturalselection has abolished these wings in spite of the opposition ofuse-inheritance, it must clearly be fully competent to reduce wingswithout its aid. In considering the rudimentary wings of the apteryx, or of the moa, emu, ostrich, &c. , we must not forget the frequent oroccasional occurrence of hard seasons, and times of drought and famine, when Nature eliminates redundant, wasteful, and ill-adapted organisms inso severe and wholesale a fashion. Where enemies are absent there wouldbe unrestrained multiplication, and this would greatly increase theseverity of the competition for food, and so hasten the elimination ofdisused and useless parts. DROOPING EARS AND DETERIORATED INSTINCTS. Mr. Galton has pointed out that existing races and existing organs areonly kept at their present high pitch of organic excellence by thestringent and incessant action of natural or artificial selection; andthe simple relaxation or withdrawal of such selective influences willalmost necessarily result in a certain amount of deterioration, independently even of the principle of economy. [21] I think that thiscessation of a previous selective process will account for thedrooping--but _not diminished_--ears of various domesticated animals(human preference and increased weight evidently aiding), and also forthe inferior instincts seen in them and in artificially-fed caterpillarsof the silk-moth, which now "often commit the strange mistake ofdevouring the base of the leaf on which they are feeding, andconsequently fall down. " Anyhow, I fail to see that anything is provedby this latter case, except that natural instinct may be perverted oraborted under unnatural conditions and a changed method of selectionwhich abolishes the powerful corrective formerly supplied by naturalselection. WINGS AND LEGS OF DUCKS AND FOWLS. The reduced wings and enlarged legs of domesticated ducks and fowls areattributed by Darwin and Spencer to the inheritance of the effects ofuse and disuse. But the inference by no means follows. Natural selectionwould usually favour these adaptive changes, and they would also havebeen aided by an artificial selection which is often unconscious orindirect. Birds with diminished power of flight would be less difficultto keep and manage, and in preserving and multiplying such birds manwould be unconsciously bringing about structural changes which wouldeasily be regarded as effects of use and disuse. "About eighteencenturies ago Columella and Varro speak of the necessity of keepingducks in netted enclosures like other wild fowl, so that at this periodthere was danger of their flying away. "[22] Is it not probable that thebest fliers would escape most frequently, or would pine most if keptconfined? On the other hand, birds with lessened powers of flight wouldnot be eliminated as under natural conditions, but would be favoured;and natural selection, together with artificial selection of the mostflourishing birds, would thicken and strengthen the legs to meetincreased demands upon them. The diminution of the duck's wing is not great even in the birds that"never fly, " and from this we must deduct the direct effect of disuse onthe individual during its lifetime. As Weismann suggests, the_inherited_ portion of the change could only be ascertained by comparingthe bones, &c. , of wild and tame ducks _similarly reared_. If individualdisuse diminished the weight of the duck's wing-bones by 9 per cent. There would be nothing left to account for. I suspect that investigation would reveal anomalies inconsistent withthe theory of use-inheritance. Thus according to Darwin's tables ofcomparative weights and measurements[23] the leg-bones of the Penguinduck have slightly diminished in length, although they have increased 39per cent. In weight. Relatively to the weight of the skeleton, theleg-bones have shortened in the tame breeds of ducks by over 5 per cent. (and in two breeds by over 8 per cent. ) although they have increasedmore than 28 per cent. In proportional weight. [24] How can increased usesimultaneously shorten and thicken these bones? If the relativeshortening is attributed to a heavier skeleton, then the apparentlyreduced weight of the wing-bones is fully accounted for by the samecircumstance, and disuse has had no inherited effect. Another strange circumstance is that the wing-bones have diminished _inlength only_. The shortening is about 6 per cent. More than in theshortened legs, and it amounts to 11 per cent. As compared with theweight of the skeleton. Such a shortening should represent a reductionof 29 per cent. In weight, whereas the actual reduction in the weight ofthe wing-bones relatively to the weight of the skeleton is only 9 percent. Even in the breeds that never fly. Independently of shortening, the disused wing-bones have actually thickened or increased in weight. In the Aylesbury duck the disproportion caused by these conflictingchanges is so great that the wing-bones are 47 per cent. Heavier thanthey should be if their weight had varied proportionally with theirlength. [25] The reduction in weight on which Darwin relies seems to beentirely due to the shortening, and this shortening appears to beirrelevant to disuse, since the wings of the Call duck are similarlyshortened in their proportions by 12 per cent. , although this birdhabitually flies to such an extent that Darwin partly attributes thegreatly increased weight of its wing-bones to increased use underdomestication. We find that _all_ the changes are in the direction of shorter andthicker bones--a tendency which must be largely dependent upon thesuspension of the rigorous elimination which keeps the bones of thewild duck _long and light_. The used leg-bones and the disusedwing-bones have alike been shortened and thickened, though in differentproportions. Natural or artificial selection might easily thicken legswithout lengthening them, or shorten wings without eliminating strongheavy bones, but it can hardly be contended that use-inheritance hasacted in such conflicting ways. The thickening of the wing-bones hasactually more than kept pace with any increase of weight in theskeleton, in spite of the effect of individual disuse and of the allegedcumulative effect of ancestral disuse for hundreds of generations. Thecase of the duck deserves special attention as a crucial one, if onlyfrom the fact that in this instance, and in this instance only, hasDarwin given the weights of the skeletons, thus furnishing the means fora closer examination of his details than is usually possible. If we ignore such factors as selection, panmixia, correlation, and theeffects of use and disuse during lifetime, and still regard the case ofthe domestic duck as a valid proof of the inheritance of the effects ofuse and disuse, we must also accept it as an equally valid proof thatthe effects of use and disuse are _not_ inherited. Nay, we may even haveto admit that, in two points out of four, the _inherited_ effect of useand disuse on successive generations is exactly opposite to theimmediate effect on the individual. Among fowls the wing-bones have lost much in weight but little ornothing in length--which is the reverse of what has occurred in ducks, although disuse is alleged to be the common cause in both cases. Some ofthe fowls which fly least have their wing-bones as long as ever. In thecase of the Silk and Frizzled fowls--ancient breeds which "cannot fly atall"--and in that of the Cochins, which "can hardly fly up to a lowperch, " Darwin observes "how truly the proportions of an organ may beinherited although not fully exercised during many generations. "[26] Infour out of twelve breeds the wing-bones had become slightly heavierrelatively to the leg-bones. Do not these facts tend to show that thechanges in fowls' wings are due to fluctuating variability and selectiveinfluences rather than to a general law whereby the effects of disuseare cumulatively inherited? PIGEONS' WINGS. Concerning pigeons' wings Darwin says: "As fancy pigeons are generallyconfined in aviaries of moderate size, and as even when not confinedthey do not search for their own food, they must during many generationshave used their wings incomparably less than the wild rock-pigeon . .. But when we turn to the wings we find what at first appears a whollydifferent and unexpected result. "[27] This unexpected increase in thespread of the wings from tip to tip is due to the feathers, which havelengthened in spite of disuse. Excluding the feathers, the wings wereshorter in seventeen instances, and longer in eight. But as artificialselection has lengthened the wings in some instances, why may it nothave shortened them in others? Wings with shortened bones would fold upmore neatly than the long wings of the Carrier pigeon for instance, andso might unconsciously be favoured by fanciers. The selection of elegantbirds with longer necks or bodies would cause a relative reduction inthe wings--as with the Pouter, where the wings have been greatlylengthened but not so much as the body. [28] Slender bodies, too, and thelessened divergence of the furculum, [29] would slightly diminish thespread of the wings, and so would affect the measurements taken. As thewing-bones, moreover, are to some extent correlated with the beak andthe feet, the artificial selection of shortened beaks might tend toshorten the wing as well as the feet. Under these circumstances how canwe be sure of the actual efficacy of use-inheritance? Surely selectionis as fully competent to effect slight changes in the direction ofuse-inheritance as it undoubtedly is to effect great changes in directopposition to that alleged factor of evolution. SHORTENED BREAST-BONE IN PIGEONS. The shortening of the sternum in pigeons is attributed to disuse of theflight muscles attached to it. The bone is only shortened by a third ofan inch, but this represents a very remarkable reduction in proportionallength, which Darwin estimates at from one-seventh to one-eighth, orover 13 per cent. This marked reduction, too, quite unlike the slightreduction of the wing-bones to which the other ends of the muscles areattached, was universal in the eleven specimens measured by Darwin; andthe bone, though acknowledged to have been modified by artificialselection in some breeds, is not so open to observation as wings orlegs. Even, however, if this relative shortening of the sternum remainedotherwise inexplicable, it might still be as irrelevant to use anddisuse as is the fact that "many breeds" of fancy pigeons have lost arib, having only seven where the ancestral rock-pigeon has eight. [30]But the excessive reduction in the sternum is far from beinginexplicable. In the first place Darwin has somewhat over-estimated it. Instead of comparing the deficiency of length with the increased lengthwhich _should_ have been acquired (since the pigeons have increased inaverage size) he compares it with the length of the breast-bone in therock-pigeon. [31] By this method if a pigeon had doubled in dimensionswhile its breast-bone remained unaltered, the reduction would be putdown as 100 per cent. , whereas obviously the true reduction would beone-half, or 50 per cent. Of what the bone _should be_. Avoiding thiserror and a minor fallacy besides, a sound estimate reduces the supposedreduction of 13 or 14 per cent. To one of 11·7 per cent. , which is stillof course a considerable diminution. Part of this reduction must be due to the direct effect of disuse duringthe lifetime of the individual. Another and perhaps very considerablepart of the relative change must be attributed to the lengthening of theneck or body by artificial selection, or to other modifications ofshape and proportion effected directly or indirectly by the samecause. [32] The reduction is greatest in the Pouter (18-1/2 per cent. )and in the Pied Scanderoon (17-1/2 per cent. ). In the former the bodyhas been greatly elongated by artificial selection and three or fouradditional vertebræ have been acquired in the hinder part of thebody. [33] In the latter a long neck increases the length of the bird, and so causes, or helps to cause, the relative shortening of thebreast-bone. In the English Carrier--which experiences the effects ofdisuse, as it is too valuable to be flown--the relative reduction of 11per cent. Is apparently more than accounted for by the "elongatedneck. " The Dragon also has a long neck. In the Pouter, although thebreast-bone has been shortened by 18-1/2 per cent. Relatively to thelength of the body, it has _lengthened_ by 20 per cent. Relatively tothe _bulk_ of the body. [34] Darwin forgot to ask whether allowance mustnot be made for a frequent, or perhaps general, elongation of the neckand the hinder part of the body, and the relative shortening or thethrowing forward of the central portion containing the ribs (frequentlyone less in number) and the sternum. The whole body of the pigeon is somuch under the control of artificial selection, that every precautionmust be taken to guard against such possible sources of error. [35] Under domestication there would be a suspension of the previouselimination of reduced breast-bones by natural selection (Weismann'spanmixia), and a diminution of the parts concerned in flying might evenbe favoured, as lessened powers of _continuous_ flight would preventpigeons from straying too far, and would fit them for domestication orconfinement. Such causes might reduce some of the less observed partsaffected by flying, while still leaving the wing of full size foroccasional flight, or to suit the requirements of the pigeon-fanciers. Achange might thus be commenced like that seen in the rudimentary keel ofthe sternum in the owl-parrot of New Zealand, which has lost the powerof flight although still retaining fairly-developed wings. SHORTENED FEET IN PIGEONS. Darwin thinks it highly probable that the short feet of most breeds ofpigeons are due to lessened use, though he owns that the effects ofcorrelation with the shortened beak are more plainly shown than theeffects of disuse. [36] But why need the inherited effects of disuse becalled in to explain an average reduction of some 5 per cent. , whenDarwin's measurements show that in the breeds where long beaks arefavoured the principle of correlation between these parts has lengthenedthe foot by 13 per cent. In spite of disuse? SHORTENED LEGS OF RABBITS. In the case of the domestic rabbit Darwin notices that the bones of thelegs have (relatively) become shorter by an inch and a half. But as theleg-bones have _not_ diminished in relative weight, [37] they mustclearly have grown _thicker_ or denser. If disuse has shortened them, asDarwin supposes, why has it also thickened them? The ears and the tailhave been lengthened in spite of disuse. Why then may not the ungainlyhind-legs have been shortened by human preference independently of theinherited effects of disuse? By relying on apparently favourableinstances and neglecting the others it would be easy to arrive at allmanner of unsound conclusions. We might thus become convinced thatvessels tend to sail northwards, or that a pendulum oscillates moreoften in one direction than in the other. It must not be forgotten thatit would be easy to cite an enormous number of cases which are in directconflict with the supposed law of use-inheritance. BLIND CAVE-ANIMALS. Weak or defective eyesight is by no means rare as a spontaneousvariation in animals, "the great French veterinary Huzard going so faras to say that a blind race [of horses] could soon be formed. " Naturalselection evolves blind races whenever eyes are useless ordisadvantageous, as with parasites. This may apparently be doneindependently of the effects of disuse, for certain neuter ants haveeyes which are reduced to a more or less rudimentary condition, andneuter termites are blind as well as wingless. In one species of ant(_Eciton vastator_) the sockets have disappeared as well as the eyes. Indeep caves not only would natural selection cease to maintain goodeyesight but it would persistently favour blindness--or the entireremoval of the eye when greatly exposed, as in the cave-crab--and as Dr. Ray Lankester has indicated, [38] there would have been a previousselection of animals which through spontaneous weakness, sensitiveness, or other affection of the eye found refuge and preservation in the cave, and a subsequent selection of the descendants whose fitness for relativedarkness led them deeper into the cave or prevented them from strayingback to the light with its various dangers and severer competition. Panmixia, however, as Weismann has shown, would probably be the mostimportant factor in causing blindness. INHERITED HABITS. Darwin says: "A horse is trained to certain paces, and the colt inheritssimilar consensual movements. "[39] But selection of the constitutionaltendency to these paces, and imitation of the mother by the colt, mayhave been the real causes. The evidence, to be satisfactory, should showthat such influences were excluded. Men acquire proficiency in swimming, waltzing, walking, smoking, languages, handicrafts, religious beliefs, &c. , but the children only appear to inherit the innate abilities orconstitutional proclivities of their parents. Even the songs of birds, including their call-notes, are no more inherited than is language byman (_Descent of Man_, p. 86). They are learned from the parent. Nestlings which acquire the song of a distinct species, "teach andtransmit their new song to their offspring. " If use-inheritance has notfixed the song of birds, why should we suppose that in a singlegeneration it has transmitted a newly-taught method of walking ortrotting? It is alleged that dogs inherit the intelligence acquired by associationwith man, and that retrievers inherit the effects of theirtraining. [40] But selection and imitation are so potent that theadditional hypothesis of use-inheritance seems perfectly superfluous. Where intelligence is not highly valued and carefully promoted byselection, the intelligence derivable from association with man does_not_ appear to be inherited. Lap-dogs, for instance, are oftenremarkably stupid. Darwin also instances the inheritance of dexterity in seal-catching as acase of use-inheritance. [41] But this is amply explained by the ordinarylaw of heredity. All that is needed is that the son shall inherit thesuitable faculties which the father inherited before him. TAMENESS OF RABBITS. Darwin holds that in some cases selection alone has modified theinstincts and dispositions of domesticated animals, but that in mostcases selection and the inheritance of acquired habits have concurred ineffecting the change. "On the other hand, " he says, "habit alone in somecases has sufficed; hardly any animal is more difficult to tame than theyoung of the wild rabbit; scarcely any animal is tamer than the young ofthe tame rabbit; but I can hardly suppose that domestic rabbits haveoften been selected for tameness alone; so that we must attribute atleast the greater part of the inherited change from extreme wildness toextreme tameness to habit and long-continued close confinement. "[42] But there are strong, and to me irresistible, arguments to the contrary. I think that the following considerations will show that the greaterpart, if not the whole, of the change must be attributed to selectionrather than to the direct inheritance of acquired habit. (1) For a period which may cover thousands of generations, there hasbeen an entire cessation of the natural selection which maintains thewildness (or excessive fear, caution, activity, &c. ) so indispensablyessential for preserving defenceless wild rabbits of all ages from themany enemies that prey upon them. (2) During this same extensive period of time man has usually killed offthe wildest and bred from the tamest and most manageable. To some extenthe has done this consciously. "It is very conducive to successfulbreeding to keep only such as are quiet and tractable, " says anauthority on rabbits, [43] and he enjoins the selection of thehandsomest and _best-tempered_ does to serve as breeders. To a stillgreater extent man has favoured tameness unconsciously and indirectly. He has systematically selected the largest and most prolific animals, and has thus doubled the size and the fertility of the domestic rabbit. In consciously selecting the largest and most flourishing individualsand the best and most prolific mothers, he _must_ have unconsciouslyselected those rabbits whose relative _tameness_ or placidity ofdisposition rendered it possible for them to flourish and to produce andrear large and thriving families, instead of fretting and pining as thewilder captives would do. When we consider how exceedingly delicate andeasily disturbed yet all-important a function is that of maternity inthe continually breeding rabbit, we see that the tamest and the leastterrified would be the most successful mothers, and so would continuallybe selected, although man cared nothing for the tameness in itself. Thetamest mothers would also be less liable to neglect or devour theiroffspring, as rabbits commonly do when their young are handled too soon, or even when merely frightened by mice, &c. , or disturbed by changedsurroundings. (3) We must remember the extraordinary fecundity of the rabbit and theexcessive amount of elimination that consequently takes place eithernaturally or artificially. Where nature preserved only the wildest, manhas preserved the tamest. If there is any truth in the Darwinian theory, this thorough and long-continued reversal of the selective process_must_ have had a powerful effect. Why should it not be amply sufficientto account for the tameness and mental degeneracy of the rabbit withoutthe aid of a factor which can readily be shown to be far weaker in itsnormal action than either natural or artificial selection? Why may notthe tameness of the rabbit be transferred to the group of cases inwhich Darwin holds that "habit has done nothing, " and selection has doneall? (4) If use-inheritance has tamed the rabbit, why are the bucks still somischievous and unruly? Why is the Angora breed the only one in whichthe males show no desire to destroy the young? Why, too, shoulduse-inheritance be so much more powerful in the rabbit than with otheranimals which are far more easily tamed in the first instance? Wildyoung rabbits when domesticated "remain unconquerably wild, " and, although they may be kept alive, they pine and "rarely come to anygood. " Yet the animal which _acquires_ least tameness--or apparently, indeed, none at all--inherits most! It appears, in fact, to inherit thatwhich it cannot acquire--a circumstance which indicates the selection ofspontaneous variations rather than the inheritance of changed habits. Such variations occasionally occur in animals in a marked degree. Of alitter of wolf-cubs, all brought up in the same way, "one became tameand gentle like a dog, while the others preserved their naturalsavagery. " Is it not probable that permanent domestication was renderedpossible by the inevitable selection of spontaneous variations in thisdirection? The _excessive_ tameness, too, of the young rabbit, whileeasily explicable as a result of unconscious selection, is not easilyexplained as a result of acquired habit. No particular care is taken totame or teach or domesticate rabbits. They are bred for food, or forprofit or appearance, and they are left to themselves most of theirtime. As Sir J. Sebright notices with some surprise, the domestic rabbit"is not often visited, and seldom handled, and yet it is always tame. " MODIFICATIONS OBVIOUSLY ATTRIBUTABLE TO SELECTION. Innumerable modifications in accordance with altered use or disuse, suchas the enlarged udders of cows and goats, and the diminished lungs andlivers in highly bred animals that take little exercise, can be readilyand fully explained as depending on selection. As the fittest for thenatural or artificial requirements will be favoured, natural orartificial selection may easily enlarge organs that are increasinglyused and economize in those that are less needed. I therefore see nonecessity whatever for calling in the aid of use-inheritance as Darwindoes, to account for enlarged udders, or diminished lungs, or the thickarms and thin legs of canoe Indians, or the enlarged chests ofmountaineers, or the diminished eyes of moles, or the lost feet ofcertain beetles, or the reduced wings of logger-headed ducks, or theprehensile tails of monkeys, or the displaced eyes of soles, or thealtered number of teeth in plaice, or the increased fertility ofdomesticated animals, or the shortened legs and snouts of pigs, or theshortened intestines of tame rabbits, or the lengthened intestines ofdomestic cats, &c. [44] Changed habits and the requisite change ofstructure will usually be favoured by natural selection; for habit, asDarwin says, "almost implies that some benefit great or small is thusderived. " SIMILAR EFFECTS OF NATURAL SELECTION AND USE-INHERITANCE. Here we perceive a difficulty which will equally trouble those whoaffirm use-inheritance and those who deny. Broadly speaking, theadaptive effects ascribed to use-inheritance coincide with the effectsof natural selection. The individual adaptability (as shown in thethickening of skin, fur, muscle, &c. , under the stimulus of friction, cold, use, &c. ) is identical in kind and direction with the racialadaptability under natural selection. Consequently the allegedinheritance of the advantageous effects of use and disuse cannot readilybe distinguished from the similarly beneficial effects of naturalselection. The indisputable fact that natural selection imitates orsimulates the beneficial effects ascribed to use-inheritance may be thechief source and explanation of a belief which may prove to bethoroughly fallacious. A similar simulation of course occurs underdomestication, where natural selection is partly replaced by artificialselection of the best adapted and therefore most flourishing animals, while in disused parts panmixia or the comparative cessation ofselection will aid or replace "economy of growth" in causingdiminution. [45] INFERIORITY OF SENSES IN EUROPEANS. "The inferiority of Europeans, in comparison with savages, in eyesightand in the other senses, " is attributed to "the accumulated andtransmitted effect of lessened use during many generations. "[46] But whymay we not attribute it to the slackened and diverted action of thenatural selection which keeps the senses so keen in some savage races? SHORT-SIGHT IN WATCHMAKERS AND ENGRAVERS. Darwin notices that watchmakers and engravers are liable to beshort-sighted, and that short-sight and long-sight certainly tend to beinherited. [47] But we must be careful not to beg the question at issueby assuming that the frequent heredity of short sight necessarily coversthe heredity of artificially-produced short-sight. Elsewhere, however, Darwin states more decisively that "there is ground for believing thatit may often originate in causes acting on the individual affected, andmay thence-forward become transmissible. "[48] This impression may arise(1) from the facts of ordinary heredity--the ancestral liability beingexcited in father and son by similar artificial habits, such as reading, and viewing objects closely as among watchmakers and engravers--or byconstitutional deterioration from indoor life, &c. , acting upon aconstitutional liability of the eye to the "something like inflammationof the coats, under which they yield" and so cause shortness of sightby altering the spherical shape of the eye-ball. (2) Panmixia, or thesuspension of natural selection, together with altered habits, willaccount for an increase of short-sight among the population generally. (3) Long-sighted people could not work at watchmaking and engraving socomfortably and advantageously as at other occupations, and hence wouldbe less likely to take to such callings. LARGER HANDS OF LABOURERS' INFANTS. [49] These are best explained as the result of natural selection and of thediminution of the hand by sexual selection in the gentry. If the largerhands of labourers' infants are really due to the inherited effects ofancestral use, why does the development occur so early in life, insteadof only at a corresponding period, as is the rule? During the first fewyears of its life, at least, the labourer's infant does no more workthan the gentleman's child. Why are not the effects of this disuseinherited by the labourer's infant? If the enlargement of the infant'shand illustrates the transference of a character gained later in life, it is evident that the transference must take place in spite of theinherited effects of disuse. THICKENED SOLE IN INFANTS. Darwin also attributes the thickened sole in infants, "long beforebirth, " to "the inherited effects of pressure during a long series ofgenerations. "[50] But disuse should make the infant's sole _thin_, andit is this thinness that should be inherited. If we suppose theinheritance of the thickened soles of later life to be transferred to anearlier period, we have the anomaly of the inherited effects of disuseat that earlier period being overpowered by the untimely inheritance ofthe effects of use at another. On the other hand, it is clear thatnatural selection would favour thickened soles for walking on, and mightalso promote an early development which would ensure their being readyin good time for actual use; for variations in the direction of delaywould be cut off, while variations in the other direction would bepreserved. Anyhow, the mere transference of a character to an earlierperiod is no proof of use-inheritance. The real question is whether thethickened sole was gained by natural selection or by the inheritedeffects of pressure, and the mere transference or hastened appearance ofthe thickening does not in any degree solve this question. It merelyexcludes the effect of disuse during lifetime, and thus presents afallacious appearance of being decisive. The thickened sole of theunborn infant, however, like the lanugo or hairy covering, is probably aresult of the direct inheritance of ancestral stages of evolution, ofwhich the embryo presents a condensed epitome. While the relativethinness of the infant's sole might be pointed to as the effect of_disuse_ during a long series of generations, its thickness is rather anillustration of atavism still resisting the effects of long-continueddisuse. There is nothing to show that the inheritable portion of thefull original thickness was not gained by natural selection rather thanby the directly inherited effect of use; and the latter, beingcumulative and indiscriminative in its action, would apparently havemade the sole very much thicker and harder than it is. If naturalselection were not supreme in such cases, how could we account for theeffects of pressure resulting in hard hoofs in some cases and only softpads in others? A SOURCE OF MENTAL CONFUSION. Of course in a certain sense this thickening of the sole has resultedfrom use. In one sense or other, most--or perhaps all--of the results ofnatural selection are inherited effects of use or disuse. Naturalselection preserves that which is of use and which is used, while iteliminates that which is useless and is not used. The most confidentassertions of the effects of use and disuse in modifying the heritabletype, appear to rest on this indefeasible basis. Darwin's statementsconcerning the effects of use and disuse in evolution can frequently beread in two senses. They often command assent as undeniable truisms asthey stand, but are of course written in another and more debatablesense. Thus in the case of the shortened wings and thickened legs of thedomestic duck, I believe equally with Darwin and Spencer that "no onewill dispute that they have resulted from the lessened use of the wingsand the increased use of the legs. " "Use" is at bottom the determiningcircumstance in evolution generally. The trunk of the elephant, the finof the fish, the wing of the bird, the cunning hand of man and hiscomplicated brain--and, in short, all organs and facultieswhatsoever--can only have been moulded and developed by use--byusefulness and by using--but not necessarily by use-inheritance, notnecessarily by directly inherited effects of use or disuse of parts inthe individual. So, too, reduced or rudimentary organs are due todisuse, but it by no means follows that the diminution is caused by anydirect tendency to the inheritance of the effects of disuse in theindividual. The effects of natural selection are commonly expressible aseffects of use and disuse, just as adaptation in nature is expressiblein the language of teleology. But use-inheritance is no more proven byone of these necessary coincidences than special design is by theother. The inevitable simulation of use-inheritance may be entirelydeceptive. Darwin thinks that "there can be no doubt that use in our domesticanimals has strengthened and enlarged certain parts, and disusediminished them; and that such modifications are inherited. " Undoubtedly"such" or _similar_ modifications have often been inherited, but how canDarwin possibly tell that they are not due to the simulation ofuse-inheritance by natural or artificial selection acting upon generalvariability? Of the inevitability of selection and of its generallyadaptive tendencies "there can be no doubt, " and panmixia would tend toreduce disused parts; so that there _must always_ remain grave doubts ofthe alleged inheritance of the similar effects of use and disuse, unlesswe can accomplish the extremely difficult feat of excluding both naturaland artificial selection as causes of enlargement, and panmixia andselection as causes of dwindling. WEAKNESS OF USE-INHERITANCE. Use-inheritance is normally so weak that it appears to be quite helplesswhen opposed to any other factor of evolution. Natural selection evolvesand maintains the instincts of ants and termites in spite ofuse-inheritance to a more wonderful degree than it evolves the instinctsof almost any other animal with the fullest help of use-inheritance. Itdevelops seldom-used horns or natural armour just as readily asconstantly-used hoofs or teeth. Sexual selection evolves elaboratestructures like the peacock's tail in spite of disuse and naturalselection combined. Artificial selection appears to enlarge or diminishused parts or disused parts with equal facility. The assistance ofuse-inheritance seems to be as unnecessary as its opposition isineffective. The alleged inheritance of the effects of use and disuse in our domesticanimals must be very slow and slight. [51] Darwin tells us that "thereis no good evidence that this ever follows in the course of a singlegeneration. " "Several generations must be subjected to changed habitsfor any appreciable result. "[52] What does this mean? One of two things. Either the tendency is very weak, or it is non-existent. If it is soweak that we cannot detect its alleged effects till several generationshave elapsed, during which time the more powerful agency of selectionhas been at work, how are we to distinguish the effects of the minorfactor from that of the major? Are we to conclude that use-inheritance_plus_ selection will modify races, just as Voltaire firmly held thatincantations, together with sufficient arsenic, would destroy flocks ofsheep? Is it not a significant fact that the alleged instances ofuse-inheritance so often prove to be self-conflicting in their details? For satisfactory proof of the prevalence of a law of use-inheritance werequire normal instances where selection is clearly inadequate toproduce the change, or where it is scarcely allowed time or opportunityto act, as in the immediate offspring of the modified individual. Of thefirst kind of cases there seems to be a plentiful lack. Of the latterkind, according to Darwin, there appears to be none--a circumstancewhich contrasts strangely and suspiciously with the many decisive casesin which variation from unknown causes has been inherited moststrikingly in the immediate offspring. It must be expected, indeed, thatamong these innumerable cases some will accidentally mimic the allegedeffects of use-inheritance. If Darwin had felt certain that the effects of habit or use tended inany marked degree to be conveyed directly and cumulatively to succeedinggenerations, he could hardly have given us such cautious, half-heartedencouragement of good habits as the following:--"It is not improbablethat after long practice virtuous tendencies may be inherited. " "Habits, moreover followed during many generations probably tend to beinherited. "[53] This is probable, independently of use-inheritance. The"many generations" specified or implied, will allow time for the play ofselective as well as of cumulatively-educative influences. There mustapparently be a constitutional or inheritable predisposition or fitnessfor the habits spoken of, which otherwise would scarcely be continuedfor many generations, except by the favourably-varying branches of afamily: which again is selection rather than use-inheritance. Where is the necessity for even the remains of the Lamarckian doctrineof inherited habit? Seeing how powerful the general principle ofselection has shown itself in cases where use-inheritance could havegiven no aid or must even have offered its most strenuous opposition, why should it not equally be able to develop used organs or repressdisused organs or faculties without the assistance of a relatively weakally? Selection evolved the remarkable protective coverings of thearmadillo, turtle, crocodile, porcupine, hedgehog, &c. ; it formed alikethe rose and its thorn, the nut and its shell; it developed thepeacock's tail and the deer's antlers, the protective mimicry of variousinsects and butterflies, and the wonderful instincts of the white ants;it gave the serpent its deadly poison and the violet its grateful odour;it painted the gorgeous plumage of the Impeyan pheasant and thebeautiful colours and decorations of countless birds and insects andflowers. These, and a thousand other achievements, it has evidentlyaccomplished without the help of use-inheritance. Why should it bethought incapable of reducing a pigeon's wing or enlarging a duck'sleg? Why should it be credited with the help of an officious ally ineffecting comparatively slight changes, when great and strikingmodifications are effected without any such aid? FOOTNOTES: [15] Weismann's _Essays on Heredity_, &c. Clarendon Press, 1889. [16] _Life and Letters_, i. P. 16. Darwin's reverence for his father"was boundless and most touching. He would have wished to judgeeverything else in the world dispassionately, but anything his fatherhad said was received with almost implicit faith; . .. He hoped none ofhis sons would ever believe anything because he said it, unless theywere themselves convinced of its truth--a feeling in striking contrastwith his own manner of faith" (_Life and Letters_, i. Pp. 10, 11). [17] _Ibid. _, i. P. 38. [18] _Life and Letters_, ii. P. 14. [19] _Origin of Species_, pp. 117, 118. [20] _Ibid. _, p. 180. [21] _Contemporary Review_, December, 1875, pp. 89, 93. [22] _Variation of Animals and Plants under Domestication_, i. 292. [23] _Variation of Animals and Plants under Domestication_, i. 299-301. [24] To keep pace with this lateral increase in weight, the leg-bonesshould have lengthened considerably so that their total deficiency inproportional length is 17 per cent. , --a changed proportion which being_linear_ is more excessive than the increase of weight by 28 per cent. So marked is the effect of the combined thickening and shortening thatin the Aylesbury breed--which is the most typically representativeone--the leg-bones have become 70 per cent. Heavier than they should beif their thickness had continued to be proportional to their length. [25] This excessive thickening under disuse appears to be due partly toa positive lateral enlargement or increase of proportional weight ofabout 7-1/2 per cent. , and partly to a shortening of about 15 per cent. Carefully calculated, the reduction of the weight of the wing-bones inthis breed is only 8·3 per cent. Relatively to the whole skeleton, oronly 5 per cent. Relatively to the skeleton _minus_ legs and wings. Thelatter method is the more correct, since the excessive weight of theleg-bones increases the weight of the skeleton more than the diminishedweight of the wing-bones reduces it. [26] _Variation of Animals and Plants under Domestication_, i. 284. [27] _Variation of Animals and Plants under Domestication_, i. 184, 185. [28] _Ibid. _, i. 144, 145. [29] _Ibid. _, i. 185. [30] _Variation of Animals and Plants under Domestication_, i. 175. [31] _Variation of Animals and Plants under Domestication_, i. 184. Isuspect that Darwin was in poor health when he wrote this page. He nodsat least four times in it. Twice he speaks of "twelve" breeds where heobviously should have said eleven. [32] If a prominent breast is admired and selected by fanciers, thesternum might shorten in assuming a more forward and vertical position. If the shortening of the sternum is entirely due to disuse, it seemsstrange that Darwin has not noticed any similar shortening in thesternum of the duck. But selection has not tended to make the duckelegant, or "pigeon-breasted"; it has enlarged the abdominal sackinstead, besides allowing the addition of an extra rib in various cases. [33] _Variation of Animals and Plants under Domestication_, 144, 175. [34] _Variation of Animals and Plants under Domestication_, i. 179. [35] In the six largest breeds the shortening of the sternum is nearlytwice as great as in the three smaller breeds which remain nearest therock-pigeon in size. We can hardly suppose that use-inheritanceespecially affects the eight breeds that have varied most in size. If weexclude these, there is only a total shortening of 7 per cent. To beaccounted for. [36] _Variation of Animals and Plants under Domestication_, i. 183, 186. [37] _Variation of Animals and Plants under Domestication_, i. 130, 135;ii. 288. [38] _Encyclopædia Britannica_, article "Zoology. " [39] _Variation of Animals and Plants under Domestication_, ii. 367. [40] _Variation of Animals and Plants under Domestication_, ii. 367. Whythen does the cheetah inherit ancestral habits so inadequately that itis useless for the chase unless it has first learned to hunt for itselfbefore being captured? (ii. 133). [41] _Descent of Man_, p. 33. [42] _Origin of Species_, pp. 210, 211. [43] E. S. Delamer on _Pigeons and Rabbits_, pp. 132, 103. For otherpoints referred to, see pages 133, 102, 100, 95, 131. [44] _Origin of Species_, pp. 188, 110; _Descent of Man_, pp. 32-35;_Variation of Animals and Plants under Domestication_, ii. 289, 293. Useor disuse during lifetime of course co-operates, and in some cases, asin that of the canoe Indians, may be the principal or even perhaps the_sole_ cause of the change. [45] For the importance of panmixia as invalidating Darwin's strongestevidence for use-inheritance--namely, that drawn from the effects ofdisuse in highly-fed domestic animals where there is supposed to be noeconomy of growth--see Professor Romanes on Panmixia, _Nature_, April 3, 1890. [46] _Descent of Man_, p. 33. [47] _Descent of Man_, p. 33. [48] _Variation of Animals and Plants under Domestication_, i. , 453. [49] _Descent of Man_, p. 33. [50] _Descent of Man_, p. 33. [51] Wallace shows that the changes in our domestic animals, if spreadover the thousands of years since the animals were first tamed, must beextremely insignificant in each generation, and he concludes that suchinfinitesimal effects of use and disuse would be swallowed up by the fargreater effects of variation and selection (_Darwinism_, p. 436). Professor Romanes has replied to him in the _Contemporary Review_(August 1889), showing that this is no disproof of the existence of theminor factor, inasmuch as slight changes in each generation need notnecessarily be matters of life and death to the individual, althoughtheir cumulative development by use-inheritance might eventually becomeof much service. But selection would favour spontaneous variations of asimilarly serviceable character. The slightest tendency to eliminate theextreme variations in either direction would proportionally modify theaverage in a breed. Use-inheritance appears to be so relatively weak afactor that probably neither proof nor disproof of its existence canever be given, owing to the practical impossibility of disentangling itseffects (if any) from the effects of admittedly far more powerfulfactors which often act in unsuspected ways. Thus wild ducklings, whichcan easily be reared by themselves, invariably "die off" if reared withtame ones (_Variation_, &c. , i. 292, ii. 219). They cannot get theirfair share in the competition for food, and are completely eliminated. Professor Romanes fully acknowledges that there is the "gravest possibledoubt" as to the transmission of the effects of disuse (Letter onPanmixia, _Nature_, March 13, 1890). [52] _Variation of Animals and Plants under Domestication_, ii. 287-289. [53] _Descent of Man_, pp. 612, 131. INHERITED INJURIES. INHERITED MUTILATIONS. The almost universal _non-inheritance_ of mutilations seems to me a farmore valid argument _against_ a general law of modification-inheritancethan the few doubtful or abnormal cases of such inheritance can furnishin its favour. No inherited effect has been produced by the docking ofhorses' tails for many generations, or by a well-known mutilation whichhas been practised by the Hebrew race from time immemorial. As lost ormutilated parts are reproduced in offspring independently of theexistence of those parts in the parent, there is the less reason tosuppose that the particular condition of parental parts transmitsitself, or tends to transmit itself, to the offspring. So unsatisfactoryis the argument derivable from inherited mutilations that Mr. Spencerdoes not mention them at all, and Darwin has to attribute them to aspecial cause which is independent of any general theory ofuse-inheritance. [54] Darwin's most striking case--and to my mind the only case of anyimportance--is that of Brown-Séquard's epileptic guinea-pigs, whichinherited the mutilated condition of parents who had gnawed off theirown gangrenous toes when anæsthetic through the sciatic nerve havingbeen divided. [55] Darwin also mentions a cow that lost a horn byaccident, followed by suppuration, and subsequently produced threecalves which had on the same side of the head, instead of a horn, a bonylump attached merely to the skin. Such cases may seem to prove thatmutilation _associated with morbid action_ is occasionally inherited orrepeated with a promptitude and thoroughness that contrast moststrikingly with the imperceptible nature of the immediate inheritance ofthe effects of use and disuse; but they by no means prove thatmutilation in general is inheritable, and they are absolutely no proofwhatever of a _normal_ and non-pathological tendency to the inheritanceof acquired characters. Those who accept Darwin's special explanationof the supposed inheritance of mutilations, ought to notice that hisexplanation applies equally well under a theory which is stronglyadverse to use-inheritance--namely, Galton's idea of the sterilizationand complete "using up" of otherwise reproductive matter in the growthand maintenance of the personal structure. Darwin's explanation of inherited mutilations--which, as he notes, occur"especially or perhaps exclusively" when the injury has been followed bydisease[56]--is that all the representative gemmules which would developor repair or reproduce the injured part are attracted to the diseasedsurface during the reparative process and are there destroyed by themorbid action. [57] Hence they cannot reproduce the part in offspring. This explanation by no means implies that mutilation would _usually_affect the offspring. On the contrary, in all ordinary cases ofmutilation the purely atavistic elements or gemmules would be set freefrom any modifying influence of the non-existent or mutilated part. Thegemmules--as in Galton's theory of heredity and with neuterinsects--might be perfectly independent of pangenesis and the normalinheritance of acquired characters. Such self-multiplying gemmuleswithout pangenesis would enable us to understand both the excessiveweakness or non-existence of normal use-inheritance, and the excessivestrength and abruptness of the effect of their partial destruction underspecial pathological conditions. The series of epileptic phenomena that can be excited by tickling acertain part of the cheek and neck of the adult guinea-pig during thegrowth and rejoining of the ends of the severed nerve, are said to berepeated with striking accuracy of detail in the young who inheritmutilated toes; but as epilepsy is often due to some _one_ excitingcause or morbid condition, the single transmission of a highly morbidcondition of the system might easily reproduce the whole chain ofconsequences and might also have caused the loss of toes. The particulars of the guinea-pig cases are very inadequatelyrecorded, [58] but the results are so anomalous[59] that Brown-Séquard'sown conclusion is that the epilepsy and the inherited injuries are_not_ directly transmitted, but that "what is transmitted is the morbidstate of the nervous system. " He thinks that the missing toes may"possibly" be exceptions to this conclusion, "but the other facts onlyimply the transmission of a morbid state of the sympathetic or sciaticnerve or of a part of the medulla oblongata. " Until we can tell what istransmitted, we are not in a position to determine whether there is anytrue inheritance or only an exaggerated simulation of it under peculiarcircumstances. When the actual observers believe that the mutilationsand epilepsy are not the cause of their own repetition, and when theseobservers guard themselves by such phrases as, "if any conclusion can atpresent be drawn from those facts, " we who have only incomplete reportsto guide us may well be excused if we preserve an even more pronouncedattitude of caution and reserve. [60] The morbid state of the system maybe wholly due to general injury of the germs rather than to specificinheritance. Weismann suggests that the morbid condition of the nervous system may bedue to some infection such as might arise from microbes, which find ahome in the mutilated and disordered nervous system in the parent, andsubsequently transmit themselves to the offspring through thereproductive elements, as the infections of various diseases appear todo--the muscardine silkworm disease in particular being known to beconveyed to offspring in this manner. But whether we can discover the true explanation or not, inheritedmutilations can hardly be accounted for as the result of a generaltendency to inherit acquired modifications. How could a factor whichseems to be totally inoperative in cases of ordinary mutilation, andonly infinitesimally operative in transmitting the normal effects of useand disuse, suddenly become so powerful as to completely overthrowatavism, and its own tendency to transmit the non-mutilated type of oneof the parents and of the non-mutilated type presented by the injuredparent in earlier life? Does not so striking and abrupt anintensification of its usually insignificant power demand an explanationwidely different from that which might account for the extremely slowand slight inheritance of the normal effects of use and disuse? Surelyit would be better to suspend one's judgment as to the true explanationof highly exceptional and purely pathological cases rather than resortto an hypothesis that creates more difficulties than it solves. THE MOTMOT'S TAIL. The narrowing of the long central tail feathers of the motmot isattributed to the inherited effects of habitual mutilation (_Descent ofMan_, pp. 384, 603). But in the specimens at South Kensington[61] thenarrowness extends upwards much beyond the habitually denuded part, andthe broadened end is the broadest part of the whole feather. If theinherited effect of an inch or two of denudation extends from three tosix inches upwards, why has it not also extended two inches downwards soas to narrow the broadened end? The narrowness seems to be a mainlyrelative or negative effect produced by the broadening out of a longtapering feather at its end under the influence of sexual selection. Several other birds have similarly narrowed or spoon-shaped feathers anddo not bite them. Is it not more feasible to suppose that thisattractive peculiarity first suggested its artificial intensification, than to suppose that the bird began nibbling without any definite cause?Sexual selection would then encourage the habit. Anyhow, it is asimpossible to show that the mutilation preceded the narrowing as it isto show that tonsure preceded baldness. OTHER INHERITED INJURIES MENTIONED BY DARWIN. Darwin quotes some cases from Dr. Prosper Lucas's "long" but weak andunsatisfactory "list of inherited injuries. "[62] But Lucas was somewhatcredulous. One of his cases is that many girls were born in Londonwithout mammæ through the injurious effect of certain corsets on themothers. He also gives a long account of a Jew who could read throughthe thick covers of a book, and whose son inherited this "hyperæsthesia"of the sense of sight in a still more remarkable degree (i. 113-119). Evidently Lucas's cases cannot be accepted without some amount ofreserve. The cases of the three calves which inherited the one-horned conditionof the cow, the two sons who inherited a father's crooked finger, andthe two sons who were microphthalmic on the same side as their fatherhad lost an eye, may be due to mere coincidence; or an inheritedconstitutional tendency or liability might lead to somewhat similarresults in parent and offspring[63]--just as the tendency to certainfatal diseases or to suicide may produce similar results in father andson, although the artificially-produced hanging or apoplexy obviouslycannot be directly transmitted. That more than one of the offspring wasaffected does not render the chances against coincidence "almostinfinitely great, " as Darwin mistakenly supposes. It "frequently occurs"that a man's sons or daughters may _all_ exhibit either a latent or anewly-developed congenital peculiarity previously unknown;[64] and thecoincidence may merely be that one of the parents accidentally suffereda similar kind of injury--a kind of coincidence which must of courseoccasionally occur, and which may have been partly caused by a latenttendency. The chances against coincidence are indeed great, but thecases appear to be correspondingly rare. Darwin acknowledges that many supposed instances of inherited mutilationmay be due to coincidence; and there is apparently no more reason forattributing inherited scars, &c. , to any special form of heredity thanto the effect of the mother's imagination on the unborn babe--a popularbut fallacious belief in corroboration of which far more allegedinstances could be collected than of the inheritance of injuries. As an instance of the coincidences that occur, I may mention that afriend of mine has a daughter who was born with a small hole in one ear, just as if it were already pierced for the earring which she has sinceworn in it. I suppose, however, that no one will venture to claim thisas an instance of the inheritance of a mutilation practised by femaleancestors, especially as such holes are not altogether unknown orinexplicable, though very rarely occurring low down in the lobe of theear. [65] Many cases are known of the inheritance of mutilations or malformationsarising congenitally from some abrupt variation in the reproductiveelements. In such cases as the one-eared rabbits, the two-legged pigs, the three-legged dogs, the one-horned stags, hornless bulls, earlessrabbits, lop-eared rabbits, tailless dogs, &c. , if the father or themother or the embryo had suffered from some accident or disease whichmight plausibly have been assigned as the cause of the originalmalformation, these transmitted defects would readily be cited asinstances of the inheritance of an accidentally-produced modification. The inheritance of exostoses on horses' legs may be the inheritance of aconstitutional tendency rather than of the effect of the parents' hardtravelling. Horses congenitally liable to such formations would transmitthe liability, [66] and this might readily be mistaken for inheritance ofthe results of the liability. An apparent increase in this liabilitymight arise from greater attention being now paid to it, or fromincreased use of harder roads; or a real increase might be due topanmixia and some obscure forms of correlation. QUASI-INHERITANCE. Of course artificially-caused ill-health or weakness in parents willtend in a general way to injure the offspring. But deterioration thuscaused is only a form of quasi-inheritance, as I should prefer to callit. Semi-starvation in a new-born babe is _not_ truly inherited from itshalf-starved mother, but is the direct result of insufficientnourishment. The general welfare of germs--as of parasites--isnecessarily bound up with that of the organism which feeds and sheltersthem, but this is not heredity, and is quite irrelevant to the questionwhether particular modifications are transmitted or not. Another form of quasi-inheritance is seen in the communication ofcertain infections to offspring. Not being transmitted by the action ofthe organism so much as in defiance of it, such diseases are not trulyhereditary, though for convenience' sake they are usually so described. A perversion or prevention of true inheritance is also seen in theaction of alcohol, or excessive overwork, or any other cause which byoriginating morbid conditions in individuals may also injure thereproductive elements. These forms of quasi-inheritance are, of course, highly important so faras the improvement of the race is concerned. So, too, is the fact thatimproved or deteriorated habits and thoughts are transmitted by personalteaching and influence and are cumulative in their effect. But all thismust not be confounded with the inheritance of acquired characters. Cases of quasi-inheritance may perhaps be most readily distinguishedfrom cases of true inheritance by the time test. When a modificationacquired in adult life is promptly communicated to the child in earlylife or from birth, it may rightly be suspected that the inheritance, like that of money or title, is not truly congenital, but is extraneousor even anti-congenital in its nature. Judged by such a standard, theinherited injuries in Brown-Séquard's guinea-pigs are only exceptionalcases of quasi-inheritance, and are not necessarily indicative of anygeneral rule affecting true inheritance. FOOTNOTES: [54] A very able anatomist of my acquaintance denies the inheritance ofmutilations and injuries, although he strongly believes in theinheritance of the effects of use and disuse. [55] _Variation of Animals and Plants under Domestication_, i. 467-469. Lost toes were only seen by Dr. Dupuy in three young out of two hundred. Obersteiner found that most of the offspring of his epilepticguinea-pigs were injuriously affected, being weakly, small, paralysed inone or more limbs, and so forth. Only two were epileptic, and both wereweakly and died early (Weismann's _Essays_, p. 311). A morbid conditionof the spinal cord might affect the hind limbs especially (as inparaplegia) and might occasionally cause loss of toes in the embryo bypreventing development or by ulceration. Brown-Séquard does not say thatthe defective feet were on the same side as in the parents (_Lancet_, Jan. , 1875, pp. 7, 8). [56] _Variation of Animals and Plants under Domestication_, ii. 57. [57] _Ibid. _, ii. 392. Perhaps it might be better to suppose that the_best_ gemmules were sacrificed in repairing the injured _nerve_, andhence only inferior substitutes were left to take their place, and couldonly imperfectly reproduce the injured part of the nervous system inoffspring. [58] Hence perhaps Mr. Spencer's error in representing the epilepticliability as permanent and as coming on _after_ healing (_Factors ofOrganic Evolution_, p. 27). [59] It is not claimed that the imperfect foot was on the same side ofthe body as in the parent, and where parents had lost _all_ the toes ofa foot, or the whole foot, the few offspring affected usually had lostonly two toes out of the three, or only a part of one or two or threetoes. Sometimes the offspring had toes missing on _both_ hind feet, although the parent was only affected in _one_. _One_ diseased ear andeye in the parent was "generally" or "always" succeeded by _two_ equallyaffected ears and eyes in the offspring (cf. _Pop. Science Monthly_, NewYork, xi. 334). The important law of inheritance at correspondingperiods was also set aside. Gangrene or inflammation commenced in bothears and both eyes soon after birth (pointing possibly to infection ofsome kind); the epileptic period commenced "perhaps two months or moreafter birth, " while the loss of toes had occurred before birth. In nocase, as Weismann points out, is the original mutilation of the nervoussystem ever transmitted. Even where an extirpated ganglion was neverregenerated in the parent, the offspring always regained the part in anapparently perfect condition. On the whole the conflicting results oughtto be as puzzling to those who may attribute them to a universaltendency to inherit the exact condition of parents as they are to thosewho, like myself, are sceptical as to the existence of such a law ortendency. [60] The various results need to be fully and impartially recorded, andthey should also be well tested and confirmed in proportion as theyappear improbable and contrary to general experience. Professor Romaneshas been carrying out the necessary experiments for some time past. [61] Natural History Museum, central hall, third recess on the left. [62] _Traité de l'Hérédité_, ii. 489; _Variation of Animals and Plantsunder Domestication_, i. 469. If injuries are inherited, why has therepeated rupture of the hymen produced no inherited effect? [63] Compare the three cases of crooked fingers given in _Variation ofAnimals and Plants under Domestication_, ii. 55, 240. [64] _Ibid. _, i. 460. Thus, where two brothers married two sisters allthe seven children were perfect albinos, although none of the parents ortheir relatives were albinos. In another case the nine children of twosound parents were all born blind (ii. 322). [65] See pp. 179-182, _Evolution and Disease_, by J. Bland Sutton, towhom and to our mutual friend Dr. D. Thurston I am indebted forinformation on various points. [66] _Variation of Animals and Plants under Domestication_, ii. 290; i. 454. MISCELLANEOUS CONSIDERATIONS. TRUE RELATION OF PARENTS AND OFFSPRING. It is difficult to entirely free ourselves from the flattering andalmost universal idea that parents are true originators or creators ofcopies of themselves. But the main truth, if not the whole truth, isthat they are merely the transmitters of types of which they and theiroffspring are alike more or less similarly moulded resultants. A parentis a trustee. He transmits, not himself and his own modifications, butthe stock, the type, the representative elements, of which he is aproduct and a custodian in one. It seems probable that he has no moredefinite or "particulate" influence over the reproductive elementswithin him than a mother over the embryo or a vessel over its cargo. Parent and offspring are like successive copies of books printed fromthe same "type. " A battered letter in the "type" will display itseffects in both earlier and later copies alike, but a purely extraneousor acquired flaw in the first copy is not necessarily repeated insubsequent copies. Unlike printer's type, however, the material sourceof heredity is of a fluctuating nature, consisting of competing elementsderived from two parents and from innumerable ancestors. Galton compares parent and child to successive pendants on the samechain. Weismann likens them to successive offshoots thrown up by a longunderground root or sucker. Such comparisons indicate the improbabilityof acquired modifications being transmitted to offspring. That parts are developed in offspring independently of those parts inparents is clear. Mutilated parents transmit parts which they do notpossess. The offspring of young parents cannot inherit the later stagesof life from parents who have not passed through them. Cases of remotereversion or atavism show that ancestral peculiarities can transmitthemselves in a latent or undeveloped condition for hundreds orthousands of generations. Many obvious facts compelled Darwin to supposethat vast numbers of the reproductive gemmules in an individual are notthrown off by his own cells, but are the self-multiplying progeny ofancestral gemmules. Galton restricts the production of gemmules by thepersonal structure to a few exceptional cases, and would evidently liketo dispense with pangenesis altogether, if he could only be sure thatacquired characters are never inherited. Weismann entirely rejectspangenesis and the inheritance of acquired characters. This enables himto explain heredity by his theory of the "Continuity of theGerm-plasm. "[67] Parent and offspring are alike successive products oroffshoots of this persistent germ-substance, which obviously would notbe correspondingly affected by modifications of parts in parents, and sowould render the transmission of acquired characters impossible. INVERSE INHERITANCE. Mr. Galton contends that the reproductive elements become sterile whenused in forming and maintaining the individual, and that only a smallproportion of them are so used. [68] He holds that the next generationwill be formed entirely, or almost entirely, from the residue ofundeveloped germs, which, not having been employed in the structure andwork of the individual, have been free to multiply and form thereproductive elements whence future individuals are derived. Hence thesingular inferiority not infrequently displayed by the children of menof extraordinary genius, especially where the ancestry has been only ofa mediocre ability. The valuable germs have been used up in theindividual, and rendered sterile in the structure of his person. Hence, too, the "strong tendency to deterioration in the transmission of everyexceptionally gifted race. " Mr. Galton's hypothesis "explains the factof certain diseases skipping one or more generations, " and it "agreessingularly well with many classes of fact;" and it is strongly opposedto the theory of use-inheritance. The elements which are used die almostuniversally without germ progeny: the germs which are _not_ used are thegreat source of posterity. Hence, when the germs or gemmules whichachieve development are either better or worse than the residue, thequalities transmitted to offspring will be of an inverse character. Ifbrain-work attracts, develops _and sterilizes_ the best gemmules, theultimate effect of education on the intellect of posterity may differfrom its immediate effect. EARLY ORIGIN OF THE OVA. As the ova are formed at as early a period as the rest of the maternalstructure, Galton notices that it seems improbable that they would becorrespondingly affected by subsequent modifications of parentalstructure. Of course it is not certain that this is a valid argument. Weknow that the paternal half of the reproductive elements does not enterthe ovum till a comparatively late stage in its history, and it is quitepossible that maternal elements or gemmules may also enter the ovum fromwithout. If reproductive elements were confined to one special part ororgan, we should be unable to explain the reproduction of lost limbs insalamanders, and the persistent effect of intercrossing on subsequentissue by the same mother, and the propagation of plants from shoots, orof the begonia from minute fragments of leaves, or the development ofsmall pieces of water-worms into complete animals. MARKED EFFECTS OF USE AND DISUSE ON THE INDIVIDUAL. These are, to some extent, an argument against the cumulativeinheritance of such effects. When a nerve atrophies from disuse, or aduct shrivels, or bone is absorbed, or a muscle becomes small or flabby, it proves, so far, that the average effect of use through enormous agesis _not_ transmitted. When the fibula of a dog's leg thickens by 400 percent. To a size "equal to or greater than" that of the removed tibiawhich previously did the work, [69] it shows that in spite of disuse forcountless generations, the "almost filiform" bone has retained apotentiality of development which is fully equal to that possessed bythe larger one which has been constantly used. When, after being rearedon the ailanthus, the caterpillars of the _Bombyx hesperus_ die ofhunger rather than return to their natural food, the inherited effect ofancestral habit does not seem to be particularly strong. Neither isthere any strongly-inherited effect of long-continued ancestral wildnessin many animals which are easily tamed. WOULD NATURAL SELECTION FAVOUR USE-INHERITANCE? If use-inheritance is really one of the factors of evolution, it iscertainly a subordinate one, and an utterly helpless one, whenever itcomes into conflict with the great ruling principle of Selection. Wouldthis dominant cause of evolution have favoured a tendency touse-inheritance if such had appeared, or would it have discouraged anddestroyed it? We have already seen that use-inheritance is unnecessary, since natural selection will be far more effective in bringing aboutadvantageous modifications; and if it can be shown that use-inheritancewould often be an evil, it then becomes probable that on the wholenatural selection would more strongly discourage and eliminate it as ahostile factor than it might occasionally favour such a tendency as atotally unnecessary aid. USE-INHERITANCE AN EVIL. Use-inheritance would crudely and indiscriminately proportion parts toactual work done--or rather to the varying _nourishment and growth_resulting from a multiplicity of causes--and this in its various detailswould often conflict most seriously with the real necessities of thecase, such as occasional passive strength, or appropriate shape, lightness and general adaptation. If its accumulated effects were notcorrected by natural or sexual selection, horns and antlers woulddisappear in favour of enlarged hoofs. The elephant's tusks would becomesmaller than its teeth. Men would have callosities for sitting on, likecertain monkeys, and huge corns or hoofs for walking on. Bones wouldoften be modified disastrously. Thus the condyle of the human jaw wouldbecome larger than the body of the jaw, because as the fulcrum of thelever it receives more pressure. Some organs (like the heart, which isalways at work) would become inconveniently or unnecessarily large. Other absolutely indispensable organs, which are comparatively passiveor are very seldom used, would dwindle until their weakness caused theruin of the individual or the extinction of the species. In eliminatingvarious evil results of use-inheritance, natural selection would beeliminating use-inheritance itself. The displacement of Lamarck's theoryby Darwin's shows that the effects of use-inheritance often differ fromthose required by natural selection; and it is clear that the latterfactor must at least have reduced use-inheritance to the very minorposition of comparative feebleness and harmlessness assigned to it byDarwin. Use-inheritance would be ruinous through causing unequal variation inco-operative parts--of which Mr. Spencer may accept his own instances ofthe jaws and teeth, and the cave-crab's lost eyes and persistenteye-stalks, as typical examples. That the variation would be unequalseems almost self-evident from the varying rapidity and extent of theeffects of use and disuse on different tissues and on different parts ofthe general structure. The optic nerve may atrophy in a few months fromdisuse consequent on the loss of the eye. Some of the bones of therudimentary hind legs of the whale are still in existence after disusefor an enormous period. Evidently use-inheritance could not equallymodify the turtle and its shell, or the brain and its skull; and inminor matters there would be the same incongruity of effect. Thus, ifthe molar teeth lengthened from extra use the incisors could not meet. Unequal and indiscriminate variation would throw the machinery of theorganism out of gear in innumerable ways. Use-inheritance would perpetuate various evils. We are taught, forinstance, that it perpetuates short-sight, inferior senses, epilepsy, insanity, nervous disorders, and so forth. It would apparently transmitthe evil effects of over-exertion, disuse, hardship, exposure, diseaseand accident, as well as the defects of age or immaturity. Would it not be better on the whole if each individual took a freshstart as far as possible on the advantageous typical lines laid down bynatural selection? Through the long stages of evolution from primævalprotoplasm upwards, such species as were least affected byuse-inheritance would be most free to develop necessary but seldom-usedorgans, protective coverings such as shells or skulls, and naturalweapons, defences, ornaments, special adaptations, and so forth; andthis would be an advantage--for survival would obviously depend on the_importance_ of a structure or faculty in deciding the struggle forexistence and reproduction, and not on the total amount of its using ornourishment. If natural selection had on the whole favoured thisofficious ally and frequent enemy, surely we should find better evidenceof its existence. Without laying undue stress upon the evil effects of use-inheritance, acareful examination of them in detail may at least serve tocounter-balance the optimistic _a priori_ arguments for belief in thatplausible but unproven factor of evolution. The benefits derivable from use-inheritance are largely illusory. Theeffects of _use_, indeed, are generally beneficial up to a certainpoint; for natural selection has sanctioned or evolved organs whichpossess the property or potentiality of developing to the right extentunder the stimulus of use or nourishment. But use-_inheritance_ wouldcumulatively alter this individual adaptability, and would tend to fixthe size of organs by the average amount of ancestral use or disuserather than by the actual requirements of the individual. Of courseunder changed conditions involving increased or lessened use of parts itmight become advantageous; but even here it may prove a decidedhindrance to adaptive evolution in some respects as well as anunnecessary aid in others. Thus in the case of animals becoming heavier, or walking more, it would _lengthen_ the legs although natural selectionmight require them to be shortened. In the Aylesbury duck and the Callduck, if use-inheritance has increased the dimensions of the bones andtendons of the leg, natural selection has had to counteract thisincrease so far as length is concerned, and to effect 8 per cent. Ofshortening besides. If use-inheritance thickens bones withoutproportionally lengthening them, it would hinder rather than help theevolution of such structures as the long light wings of birds, or thelong legs and neck of the giraffe or crane. VARIED EFFECTS OF USE AND DISUSE. The changes which we somewhat roughly and empirically group together asthe effects of "use and disuse" are of widely diverse character. Thusbone, as the physiological fact, thickens under _alternations_ ofpressure (and the consequent increased flow of nourishment), butatrophies under a steadily continued pressure; so that if the use of abone involved continuous pressure, the effect of such use would be apartial or total absorption of that bone. Darwin shows that bonelengthens as well as thickens from carrying a greater weight, whiletension (as seen in sailors' arms, which are used in pulling) appears tohave an equally marked effect in shortening bones (_Descent of Man_, p. 32). Thus different kinds of use may produce opposite results. Thecumulative inheritance of such effects would often be mischievous. Thelimbs of the sloth and the prehensile tail of the spider monkey wouldcontinually grow shorter, while the legs of the evolving elephant orrhinoceros might lengthen to an undesirable extent. Such cumulativetendencies of use-inheritance, if they exist, are obviously well keptunder by natural selection. Although the ultimate effect of use is generally growth or enlargementthrough increased flow of blood, the first effect usually is a loss ofsubstance, and a consequent diminution of size and strength. When theloss exceeds the growth, use will diminish or deteriorate the part used, while disuse would enlarge or perfect it. Teeth, claws, nails, skin, hair, hoofs, feathers, &c. , may thus be worn away faster than they canrenew themselves. But this wearing away usually stimulates the repairingprocess, and so increases the rate of growth; that is, it will increasethe size produced, if not the size retained. Which effect of use doesuse-inheritance transmit in such cases--the increased rate of growth, orthe dilapidation of the worn-out parts? We can hardly suppose that boththese effects of use will be inherited. Would shaving destroy the beardin time or strengthen it? Will the continued shearing of sheep increaseor lessen the growth of wool? What will be the ultimate effect ofplucking geese's quills, and of the eider duck's abstraction of the downfrom her breast? If the mutilated parts grow stronger or moreabundantly, why were the motmot's feathers alleged to be narrowed by theinherited effects of ancestral nibbling? The "use" or "work" or "function" of muscles, nerves, bones, teeth, skin, tendon, glands, ducts, eyes, blood corpuscles, cilia, and theother constituents of the organism, is as widely different as thevarious parts are from each other, and the effects of their use ordisuse are equally varied and complicated. USE-INHERITANCE IMPLIES PANGENESIS. How could the transmission of these varied effects to offspring beaccounted for? Is it possible to believe, with Mr. Spencer, that theeffects of use and disuse on the parts of the personal structure aresimultaneously registered in corresponding impressions on the seminalgerms? Must we not feel, with Darwin apparently, [70] that the _only_intelligible explanation of use-inheritance is the hypothesis ofPangenesis, according to which each modified cell, or physiologicalunit, throws off similarly-modified gemmules or parts of itself, whichultimately reproduce the change in offspring? If we reject pangenesis, it becomes difficult to see how use-inheritance can be possible. PANGENESIS IMPROBABLE. The more important and best-known phenomena of heredity do not requireany such hypothesis, and leading facts (such as atavism, transmission oflost parts, and the general non-transmission of acquired characters) areso adverse to it that Darwin has to concede that many of thereproductive gemmules are atavistic, and that by continuousself-multiplication they may preserve a practical "continuity ofgerm-substance, " as Weismann would term it. The idea that therelationship of offspring to parent is one of direct descent is, asGalton tells us, "wholly untenable"; and the only reason he admits somesupplementary traces of pangenesis into his "Theory of Heredity, "[71] isthat he may thus account for the more or less questionable cases of thetransmission of acquired characters. But there appears to be nonecessity even for this concession. We ought therefore to dispense withthe useless and gratuitous hypothesis that cells multiply by throwingoff minute self-multiplying gemmules, as well as by the well-knownmethod of self-division. If pangenesis occurs, the transmission ofacquired characters ought to be a prominent fact. The size, strength, health and other good or evil qualities of the cells could hardly failto exercise a marked and corresponding effect upon the size and qualityof the reproductive gemmules thrown off by those cells. The directevidence tends to show that these free gemmules do not exist. Transfusion of blood has failed to affect inheritance in the slightestdegree. Pangenesis, with its attraction of gemmules from all parts ofthe body into the germ-cells, and the free circulation of gemmules inthe offspring till they hit upon or are attracted by the particular cellor cells, with which alone they can readily unite, seems a less feasibletheory and less in conformity with the whole of the facts than anhypothesis of germ-continuity which supposes that the development of thegerm-plasm and of the successive self-dividing cells of the bodyproceeds from within. Darwin's keen analogy of the fertilization ofplants by pollen renders development from without conceivable, but asthere are no insects to convey gemmules to their destination, each kindof gemmule would have to be exceedingly numerous and easily attractedfrom amongst an inconceivable number of other gemmules. Argumentsagainst pangenesis can also be drawn from the case of neuter insects--afact which seems to have escaped Darwin's notice, although he had seenhow strongly that case was opposed to the doctrine which is theessential basis of the theory of pangenesis. SPENCER'S EXPLANATION OF USE-INHERITANCE. Mr. Spencer's explanation of the inheritance of the effects of use anddisuse (p. 36) is that "while generating a modified _consensus_ offunctions and of structures, the activities are at the same timeimpressing this modified _consensus_ on the sperm-cells and germ-cellswhence future individuals are to be produced"--a proposition which readsmore like metaphysics than science. Difficult to understand or believein ordinary instances, such _consensus_-inheritance seems impossible incases like that of the hive-bee. Can we suppose that the _consensus_ ofthe activities of the working bee impresses itself on the sperm-cellsof the drones and on the germ-cells of the carefully secluded queen?Büchner thinks so, for he says: "Although the queens and drones do notnow work, yet the capacities inherited from earlier times still remainto them, especially to the former, and are kept alive and fresh by theimpressions constantly made upon them during life, and they are thus ina position to transmit them to posterity. " Surely it is better toabandon a cherished theory than to be compelled to defend it byexplanations which are as inconsistent as they are inadequate. Newcapacities are developed as well as old ones kept fresh. The massacre orexpulsion of the drones would have to impress itself on the germ-cellsof an onlooking queen, and the imprisonment of the queen on thesperm-cells of the drones--and in such a way, moreover, as to beafterwards developed into action in the neuters only. Anduse-inheritance all the while is being thoroughly overpowered byimpression-inheritance--by the full transmission of that which is merelyseen in others! If such a law prevails, one may feel cold because anancestor thought of the frosty Caucasus. None of this absurdity wouldarise if it were clearly seen that a parent is only a trustee--thattransmission and development are perfectly distinct--that parentalmodifications are irrelevant to those transmitted to offspring. FOOTNOTES: [67] _Essays on Heredity_, p. 104. Weismann's theory is clear, simpleand convenient, but incomplete; for, unlike Darwin's theory ofpangenesis, it scarcely attempts any real explanation of the extremelycomplex potentialities possessed by the reproductive elements. Perhapswe might retain Darwin's self-multiplying gemmules without supposingthem to be thrown off by the cells, which will no longer be creditedwith _two_ modes of multiplication. These minute germs or gemmules mayhave been evolved by natural selection playing upon the sample germsthat achieve development; and they may exist either separately, or(preferably but perhaps not invariably) in aggregates to form Weismann'sgerm-plasm. [68] _Contemporary Review_, Dec. , 1875, p. 88. [69] _Variation of Animals and Plants under Domestication_, ii. 286. [70] _Variation of Animals and Plants under Domestication_, ii. 388, 398, 367; _Life and Letters_, iii. 44. [71] _Contemporary Review_, Dec. , 1875, pp. 94, 95. CONCLUSIONS. USE-INHERITANCE DISCREDITED AS UNNECESSARY, UNPROVEN, AND IMPROBABLE. General experience teaches that acquired characters are not usuallyinherited; and investigation shows that the apparent exceptions to thisgreat rule are probably fallacious. Even the alleged instances ofuse-inheritance culled by such great and judicious selectors as Darwinand Spencer break down upon examination; for they can be betterexplained without use-inheritance than with it. On the other hand, theadverse facts and considerations are almost strong enough to prove theactual non-existence of such a law or tendency. There is no need toundertake the apparently impossible task of demonstrating an absolutenegative. It will be enough to ask that the Lamarckian factor ofuse-inheritance shall be removed from the category of accredited factorsof evolution to that of unnecessary and improbable hypotheses. The mainexplanation or source of the fallacy may be found in the fact thatnatural selection frequently imitates some of the more obvious effectsof use and disuse. MODERN RELIANCE ON USE-INHERITANCE MISPLACED. Modern philanthropy--so far at least as it ever studies ultimateresults--constantly relies on this ill-founded belief as itsjustification for ignoring the warnings of those who point out theultimately disastrous results of a systematic defiance or reversal ofthe great law of natural selection. This reliance finds strong supportin Mr. Spencer's latest teachings, for he holds that the inheritance ofthe effects of use and disuse takes place universally, and that it isnow "the chief factor" in the evolution of civilized man (pp. 35, 74, iv)--natural selection being quite inadequate for the work ofprogressive modification. Practically he abandons the hope of evolutionby natural selection, and substitutes the ideal of a nation being"modified _en masse_ by transmission of the effects" of its institutionsand habits. Use-inheritance will "mould its members far more rapidly andcomprehensively" than can be effected by the survival of the fittestalone. But could we rely upon the aid of use-inheritance if it really were auniversal law and not a mere simulation of one? Let us consider some ofthe features of this alleged factor of evolution, seeing that it ishenceforth to be our principal means of securing the improvement of ourspecies and our continued adaptation to the changing conditions of aprogressive civilization. It is curiously uncertain and irregular in its action. It diminishes orabolishes some structures (such as jaws or eyes) without correspondinglydiminishing or abolishing other equally disused and closely relatedparts (such as teeth, or eye-stalks). It thickens ducks' leg-bones whileallowing them to shorten. It shortens the disused wing-bones of ducksand the leg-bones of rabbits while allowing them to thicken; and yet inother cases it greatly reduces the thickness of bones without shorteningthem. It transmits tameness most powerfully in an animal which usuallycannot acquire it. It aids in webbing the feet of water-dogs, but failsto web the feet of the water-hen or to remove the web in the feet ofupland geese. [72] It allows the disused fibula to retain a potentialityof development fully equal to that possessed by the long-used tibia. Itlengthens legs because they are used in supporting the body, andshortens arms because they are used in pulling. Whether it enlargesbrain if used in one way and diminishes it if used in another, we cannottell; but it must obviously deaden nervous sensibilities in some casesand intensify them in others. It enlarges hands long before they areused, and thickens soles long before the time for walking on them. Atthe same time, as if by an oversight, it so delays its transmission ofthe habit of walking on these thickened soles, that the gradual andtedious acquisition of the non-transmitted habit costs the infant muchtime and trouble and often some pain and danger. Yet where aided bynatural selection, as with chickens and foals, it transmits the habit inwonderful perfection and at a remarkably early date. It transmits newpaces in horses in a single generation, but fails to perpetuate thesongs of birds. It modifies offspring like parents, and yet allows theformation of two reproductive types in plants, and of two or more typeswidely different from the parents in some of the higher insects. It issaid to be indispensable for the co-ordinated development of man and thegiraffe and the elk, but appears to be unnecessary for the evolution andthe maintenance of wonderful structures and habits and instincts in athousand species of ants and bees and termites. It is the only possiblemeans of complex evolution and adaptation of co-operative parts, and yetin Mr. Spencer's most representative case it renders such importantparts as teeth and jaws unsuited for each other, and is said to ruin theteeth by the consequent overcrowding and decay. It survives amidst ageneral "lack of recognised evidence, " and only seems to act usefullyand healthily and regularly in quarters where it can least easily bedistinguished from other more powerful and demonstrable factors ofevolution. So little does it care to display its powers where they wouldbe easily verifiable as well as useful that practical breeders ignoreit. So slight is its independent power that it seems to allow naturalselection or sexual selection or artificial selection to modifyorganisms in sheer defiance of its utmost opposition, just as readily asthey modify organisms in other directions with its utmost help. If itpartially perpetuates and extends the pecked-out indentations in themotmot's tail feathers, it on the other hand fails to transmit theslightest trace of mutilation in an almost infinite number of ordinarycases, and even where the mutilation is repeated for a hundredgenerations; and it apparently repairs rather than transmits theordinary and oft-repeated losses caused by plucking hair, down andfeathers, and the wear and tear of claws, teeth, hoofs and skin. It is often mischievous as well as anomalous in its action. Undercivilization with its division of labour, the various functions of mindand body are very unequally exercised. There is overwork or misuse ofone part and disuse and neglect of others, leading to the partialbreakdown or degeneration of various organs and to general deteriorationof health through disturbed balance of the constitution. The brain, orrather particular parts of it, are often over-stimulated, while the bodyis neglected. In many ways education and civilization foster nervousnessand weakness, and undermine the rude natural health and spirits of thehuman animal. Alcohol, tobacco, tea, coffee, extra brain work, latehours, dissipation, overwork, indoor life, division of labour, preservation of the weak, and many other causes, all help to injure themodern constitution; so that the prospect of cumulative intensificationof these evils by the additional influence of use-inheritance is not anencouraging one. It is true that modern progress and prosperity areimproving the people in various respects by their direct action; but ifuse-inheritance has any share in effecting this improvement it must alsotransmit increased wants and more luxurious habits, together with suchevils as have already been referred to. As depicted by its defenders, use-inheritance transmits evils far more powerfully and promptly thanbenefits. It transmits insanity and shattered nerves rather than thehealthy brain which preceded the breakdown. It perpetuates, andcumulatively intensifies, a deterioration in the senses of civilizedmen, but it fails to perpetuate the rank vigour of various plants whentoo well nourished, or the flourishing condition of various animals whentoo fat or when tamed. It already transmits the short-sight caused by somodern an art as watchmaking, but so fails to transmit thelong-practised art of seeing (as it does of walking and talking) thatvision is worse than useless to a man until he gradually acquires thenecessary but non-transmitted associations of sensation and idea by hisown experience. In a well-known case, a blind man on gaining his sightby an operation said that "all objects seemed to touch his eyes, as whathe felt did his skin"--so little had the universal experience ofcountless ages impressed itself on his faculties. Under normal healthyconditions use-inheritance is so slow in its action that "severalgenerations" must elapse before it produces any appreciable effect, andthen that effect is only precisely what selection might be expected tobring about without its aid. Strong for evil and slow for good, it canconvey epilepsy promptly in guinea pigs, but transmits the acquirementsof genius so poorly that our best student of the heredity of genius hasto account for the frequent and remarkable deterioration of theoffspring by a theory which is strongly hostile to use-inheritance. Itwould tend to make organisms unworkable by the excessive differences inits rate and manner of action on co-operative parts, and by adaptingthese parts to the total amount of nourishment received rather than tooccasional necessity or actual usefulness. It would tend to stereotypehabits and convert reason into instinct. How then can we rely upon use-inheritance for the improvement of therace? Even if it is not a sheer delusion, it may be more detrimental asa positive evil than it is advantageous as an unnecessary benefit; andas a normal modifying agent it is miserably weak and untrustworthy incomparison with the powerful selective influences by which nature andsociety continually and inevitably affect the species for good or forevil. The effects of use and disuse--rightly directed by education inits widest sense--must of course be called in to secure the highlyessential but nevertheless _superficial, limited, and partly deceptive_improvement of individuals and of social manners and methods; but asthis artificial development of already existing potentialities does notdirectly or readily tend to become congenital, it is evident that someconsiderable amount of natural or artificial selection of the morefavourably varying individuals will still be the only means of securingthe race against the constant tendency to degeneration which wouldultimately swallow up all the advantages of civilization. The selectiveinfluences by which our present high level has been reached andmaintained may well be modified, but they must not be abandoned orreversed in the rash expectation that State education, or State feedingof children, or State housing of the poor, or any amount of Statesocialism or public or private philanthropy, will prove permanentlysatisfactory substitutes. If ruinous deterioration and other moreimmediate evils, are to be avoided, the race must still be to the swiftand the battle to the strong. The healthy Individualism so earnestlychampioned by Mr. Spencer must be allowed free play. Open competition, as Darwin teaches, with its survival and multiplication of the fittest, must be allowed to decide the battle of life independently of a foolishbenevolence that prefers the elaborate cultivation and multiplication ofweeds to the growth of corn and roses. We are trustees for the countlessgenerations of the future. 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