The Present Problem of Heredity

A LIVELY war of opinion is now in progress among the evolutionists. Following the perfect harmony which prevailed among the disciples of Darwin during the prolonged discussion aroused by the Origin of Species, this present fratricidal conflict must afford keen satisfaction to the worthy conservatives who are still nursing their doubts as to the evidence for evolution.

In a critical survey of this period from 1858 to 1880, we see that the real bond of former union did not lie in the special Darwinian hypothesis, or in any other, so much as in the general endeavor to establish a great law of organic nature. Re-reading, in this light, Huxley’s Lay Sermons and other defenses of Darwinism, one discovers that many differences of opinion as to the factors of evolution were tacitly kept in the background, in face of the common enemy. But once the great law was firmly established, these differences began to make themselves felt, and the allies slowly broke up into schools representing diverse shades of opinion. The paraphrase of a recent reviewer, “ Darwin, the Thanes fly from thee,” is clever, but misleading; for in truth some attribute far more to natural selection than Darwin did, while others by no means dispense with it. Yet, as the selection hypothesis had been the main feature of Darwin’s work, the great defection first showed itself in various degrees of dissent from his authority. At the same time, the older Lamarckian ideas of evolution began to gain ground under guise of various lines of research. The question of natural inheritance, which had been held secondary and incidental, became the main one, and it is the present problem in heredity which has finally provoked open dissension, the various schools having been hitherto comparatively harmonious.

Professor August Weismann, of Freiburg, the most brilliant and influential of modern biological essayists, enjoys the distinction of having precipitated the actual split by throwing down the glove in the contention as to the inheritance or non - inheritance of acquired characters (Vererbung der Erworbenen Eigenschaften). This has a harmless sound, yet it far exceeds in importance any problem which has come up since evolution was sub judice ; for it is at the very base of our theories, and, what is of more practical concern to most of us moderns, it profoundly affects our views and conduct of life. As Herbert Spencer says : “ I will add only that, considering the width and depth of the effects which acceptance of one or other of these hypotheses must have on our views of Life, Mind, Morals, and Politics, the question Which of them is true ? demands, beyond all other questions whatever, the attention of scientific men.”

Let us first clearly state the problem, and then follow the progress of opinion and discovery which has led up to it. To express it in familiar terms: Do children inherit solely the original constitution of their various progenitors, or do they inherit as well some of the modifications which environment and habit have exerted upon this constitution?— these latter modifications being the “ acquired characters ” of scientific language, or those which the nurture of habit and surroundings have added to the nature or original constitution of each individual. No man leaves the world as he comes into it, for, starting with certain physical and mental powers, it is inevitable that his environment will lead him to cultivate and improve some to the neglect of others, resulting, by the well-known laws of use and disuse, in corresponding hypertrophy and atrophy. If the life history, education, in short all that one does actively and passively to shape one’s mental and physical development for better or worse, are in no way reflected in the offspring, then the life of the individual is an indirect factor in the life of the race, and a direct factor only in so far as it shapes the future environment of the race. This idea becomes clearer as we proceed.

Now, if there is any principle in inheritance which has appeared self-evident and not requiring any demonstration at all, it is that acquired characters are inherited. It has been a firmly rooted belief from the earliest times, as shown by frequent allusions to it in the Old Testament, which is a perfect thesaurus of family records. It is also a widespread popular belief. In discussing the subject with laymen, I find that nine persons out of ten express surprise that there should be any doubt about the matter, and after a moment’s reflection cite a number of cases in proof, — cases, however, which are for the most part susceptible of an explanation under the supposition that acquired characters are not inherited. For example, a case of inheritance of the alcohol mania is cited: A 1 acquires the habit and dies, leaving an infant son, A 2, who is carefully guarded against temptation, yet in time, as forcibly illustrated in Ibsen’s Ghosts, develops the alcohol habit. Here is certainly an instance of the transmission of an acquired character. Upon analysis, it proves that it may be only apparently so, for we must remember that it is possible that A 1 (in this case Oswald’s father) had the alcohol mania in his original constitution, and, even if he had avoided the habit, would have transmitted it to A 2, an alternative explanation which would invalidate proof of this kind. Many similar “ proofs ” will not bear scientific analysis.

As with the Ptolemaic astronomers there were many debated points, but one law was not in question, namely, that the sun revolved around the earth, so this principle of inheritance had been an accepted dogma of specialists and the laity alike, until Weismann made his charge that it does not admit of scientific demonstration, and further claimed that all the phenomena of evolution and of life can be explained without it.

A challenge so radically affecting a long-accepted law has naturally drawn some strong expression of opinion from every modern writer upon evolution, and it is interesting to observe the manner in which various high authorities have promptly ranged themselves upon one side or the other. Upon the affirmative, including the late Charles Darwin and Moritz Wagner, we find Herbert Spencer, Professor Turner of Edinburgh, Professor Theodor Eimer of Tübingen, and the greater number of American naturalists, among whom Professor Cope is the most prominent and aggressive. Francis Galton and George Romanes occupy a somewhat neutral position ; in fact, as regards the latter, it is difficult to say exactly what his attitude is, for, apparently doubting the ability of others to understand Darwin, he has posed rather as an interpreter of the great naturalist than as an expositor of his own views. Among the avowed opponents of this doctrine, besides their leader, Weismann, is the veteran Alfred Wallace, whose recent work, Darwinism, is a plea for the omnipotency of natural selection, and to him Weismann’s theory comes as a most welcome support. Others are : Ray Lankester, a comparatively recent convert, one of the editors of Nature, recently honored by election to the much-coveted chair of zoölogy in Oxford, and noted for his quick temper in discussion ; Edward Poulton, a younger Oxonian, and translator of Weismann’s essays ; and in this country Professor Brooks, of Johns Hopkins, whose conversion to this view has more weight from the fact that his essay Heredity was devoted to exactly the opposite hypothesist. Thus we find that the older writers, with their advantage of prestige, are for the affirmative ; the present range of ability on the two sides is about balanced ; while the majority of the younger school of English naturalists, and probably many in this country who have not yet published their opinions, are on Weismann’s side. Here are workers in every field, for light comes upon the subject from all departments of biology in its broadest sense. Nor can we escape government by principles discovered among forms most remote from man; for, however opinions may differ as to our origin, none would venture to maintain the thesis that there are two modes of inheritance, — one governing man, the other the lower animals. These laws of life are of universal rule, and attach to the researches of Weismann and others a profound human interest, whether we will it or no.

The unpleasant aspect of the controversy is the extremely bitter, even personal animus of the discussion among some of the partisans. One writer has recently charged the journal Nature with being a Weismann party organ, and practically boycotting all the stronger contributions on the Lamarckian side. This, however, lends zest, and is relieved by amusing features, such as the perfect confidence displayed by both parties in their own theories, and the claims advanced by combatants on both sides to the title of the only faithful followers of the prophet Darwin.

This now disputed principle of inheritance bears the name of Lamarck; for, although he was in a measure anticipated by Buffon and Erasmus Darwin, it was the keystone of his conception of evolution, and in the concise statement of his theory found in the introduction to the Philosophic Zoölogique it forms one of the main propositions, upon which, in fact, all the others depend : —

“ Fourth law : All that has been acquired, impressed, or altered in the organization of individuals during the course of their life is preserved by generation, and transmitted to the new individuals which spring from those who have experienced these changes.” ¹

His followers, the so - called NeoLamarekians, cannot claim that the founder of their school attempted directly to prove this proposition. He simply postulated it as necessary to his theory, and advanced only indirect proof in the course of the general exposition of his views of evolution. It was to him, as to us all, one of the most obvious laws of living nature, that the race is the exponent of the action of external and internal forces upon the sum of its individuals. For this scientific faith he was willing to suffer ostracism at the hands both of the church and of his fellow zoölogists. Nevertheless, even if Lamarck’s theory as a whole had not contained this doubtful premise, and had been granted the full force he claimed, it was inadequate to account for all the phenomena. As a partial explanation of the modus operands of evolution, it simply paved the way for the substitution and rapid adoption of the far less self-evident Darwinian principle. The authority of the selection theory spread with the wonderful momentum given it by the epoch-making Origin of Species into every branch of thought upon life problems, then gradually declined until its recent revival by Weismann. It is interesting to follow, in the Life and Letters, the phases of Darwin’s confidence in the powers of natural selection, his own discovery. At first be rejected the Lamarckian doctrines, and, departing from his usual rule, wrote of them even with some contempt. Subsequently, however, his own researches, especially those upon the varieties of domestic animals, brought the Lamarckian principle home to him with the fresh force of an independent discovery, and we find him writing to Moritz Wagner : —

“ In my opinion, the greatest error which I have committed lias been not allowing sufficient weight to the direct action of the environment — that is, food, climate, etc. — independently of natural selection. Modifications thus caused, which are neither of advantage or disadvantage to the modified organism, would be especially favored, as I can now see chiefly through your observations, by isolation in a small area, where only a few individuals live under nearly uniform conditions. When I wrote the Origin of Species, and for some years afterwards, I could find little good evidence of the direct action of the environment. Now there is a large body of evidence, and your case of the Saturnia is one of the most remarkable of which I have heard.”

Darwin thus atoned for his earlier depreciation of Lamarck. Lankester has tried to put another interpretation upon this candid change of view, but Darwin’s provisional heredity hypothesis of Pangenesis, proposed at the close of the researches above mentioned, makes direct provision for the transmission of acquired characters : —

“ It is universally admitted that the cells of the body increase by self-division, thus forming the various tissues. Besides this, I assume that the cell units throw off minute granules, which are dispersed through the entire system. These may be called gemmules. They are collected from all parts of the system to form the sexual elements, and their development in the next generation forms the new being. They are thrown off by every unit not only during the adult stage, but during each stage of development of every organism. Hence it is not the reproductive organs, or buds, which generate new organisms, but the units of which each individual is composed. Gemmules are capable of transmission in a dormant state to future generations, and may then be developed.”

Observe that, according to this revival of the old idea of Democritus, every cell of the body contributes its quota to the new individual; and it follows that the peculiar life history of the cell, its greater or less activity, could not fail, in some degree, to reappear in its counterpart cell in the new being. It must strike even the lay critic that such an hypothesis of physical transmission makes scant provision for the persistent repetition of race and ancestral characters, by far the most striking feature of inheritance, and is, in fact, better adapted to Lamarck’s than to Darwin’s own views of evolution. Professor Brooks, in his essay Heredity, sought to supply this defect by the demonstration of a difference of function between the female and male cells : the former as the conservative vehicles of ancestral characters ; the latter as the progressive transmitters of the influences of environment and habit. This substitute hypothesis is opposed by the fatal difficulty of later research that there is no essential difference between the male and female cells. They are closely similar in their properties, a deduction now supported so far by experiment that the demonstration has recently been claimed of two male cells fertilizing each other and forming a new individual. As for the existence of the imaginary gemmules, Francis Galton has rendered it improbable by an ingenious experiment, showing that transfusion of blood is not accompanied by a corresponding transfer of characteristics, as we should expect if the gemmules were circulating in the system.

Thus, Pangenesis having failed in two forms even as a provisional explanation, and no attempt having been made to show how acquired characters could definitely affect the reproductive cells in such a manner as to be perpetuated in the race, the field was open for the entirely novel lines of reasoning upon this problem of genesis which Weismann has followed in reaching his beautiful and comparatively simple hypothesis of the “continuity of the germ-plasm.” “How is it,” the question resolved itself in his mind, “ that a single reproductive cell of the body can contain within itself all the hereditary tendencies of the whole organism?” The answer which he gives, after long years of research, is that the cell is not, as implied by Pangenesis, collected from the entire parental soma, or body, but is budded directly from the particular cells from which the parent itself sprang; such germ or race cells giving rise to the cells which will form the new individual, also to the new germ cells contained within it; the individuals being thus mere offshoots of a continuous chain of race cells which are, in a planetary sense, “immortal.” This race plasma has the marvelous power, inherent in all protoplasm, of imparting its properties through the course of indefinite growth and subdivision.

As “ immortal ” is a novel term in biological literature, we may digress for a moment to see what Weismann means by it. When we remember that many species have reproduced themselves for thousands of years without change, such as the sacred animals of ancient Egypt, whose embalmed bodies must in some cases be four thousand years old, we are convinced that their germ-plasm possesses to-day the same molecular strength which it had four thousand years ago; and since the amount of germ-plasm contained in a single cell must be supposed very small even within a single individual, enormous growth must occur, and thus it is not too much to say that the growth of the germ-plasm in the Egyptian ibis or crocodile in the same period must have been utterly immeasurable, its molecular strength always remaining the same.

As an illustration of Weismann’s idea of the relation of the individual to the race, recall a row of familiar forest plants, each in perfect leaf and flower, destined for a complete individual life, yet springing alike from a long continuous horizontal root beneath the surface. This root would represent the germplasm secure from all the influences which beset and mould the individual. Another illustration which occurs to me is that of the pelagic organisms, beautifully described by Agassiz, which have the power of sinking below the surface during stormy periods. Imagine the life of the individuals of such a fauna upon the surface, and their increase taking place in the still depths. This practical separation of the germ-plasm, the race, stock, blood, or whatever we call it, from the body, insulates it, so to speak, from all the changes exerted by environment and habit; there being no way in which the particular body-cell changes can affect the germ cells. Why, then, are not all individuals alike? Because each new individual represents the union of the hereditary tendencies of parents of widely different ancestry, and this chance combination of diverse constitutional traits and characteristics gives rise to favorable and unfavorable variations. It is the selection of the former by the law of survival of the fittest which steadily improves the race.

The complete chain of Weismann’s biological philosophy, then, is this: that the physical vehicle of inheritance is continuous; that variations result from the mingling of diverse ancestral characters ; that acquired characters are not inherited; that the natural selection of the fortuitous variations is sufficient to explain all the phenomena of evolution. His position as to the factors of evolution is, therefore, directly contradictory to that of Lamarck, coinciding more nearly with the earlier views of Darwin. It appears that his idea of the continuity of the race cells was in some measure anticipated, in 1880, by Professor Rauber, of Dorpat, and even earlier by Francis Galton; for the latter, in 1876, speaks of the fact that “ each individual may properly be conceived as consisting of two parts, one of which is latent, and only known to us by its effects on posterity, while the other is patent, and constitutes the person manifest to our senses.” Galton, however, did not derive the whole of the hereditary tendencies from the latent elements (which are equivalent to Weismann’s germ-plasm), but concluded that there is some contribution from the patent individual; arguing that the hereditary power in the latter case is exceedingly feeble, because the effects of the use and disuse of limbs and those of habit are transmitted to posterity in only a very slight degree. His conception of heredity was evolved from views of development substantially similar to those of Weismann, but founded exclusively upon the study of man. His latest expression of opinion (1889) on the point we are discussing is very non-committal:

“ I am unprepared to say more than a few words on the obscure, unsettled, and much-discussed subject of the possibility of transmitting ‘ acquired characters.’ The main evidence in its favor is the gradual change of the instincts of races at large in conformity with changed habits, and through their increased adaptation to their surroundings otherwise, apparently, than through the influence of natural selection.... It is, therefore, extremely difficult to say how ‘ acquired characters ’ can be inherited by their children ; it would be less difficult to conceive of their inheritance by their grandchildren.”

A few words upon Galton’s more general results so far as they bear upon this question. “ We are,” he says, “ made up bit by bit of inherited structures, like a new building composed of the fragments of an old one, — one element from this progenitor, another from that, although such elements are usually transmitted in groups.” The hereditary constitution thus made up is far stronger than the influences of nurture and education upon it. A large portion of our heritage is unused, for we transmit ancestral peculiarities we ourselves do not exhibit. Thus, a child often resembles an ancestor in some feature or character which neither of his parents apparently possessed. The ancestral contributions can, however, upon the average, be expressed in numerical terms gathered from statistics of stature. Thus, contributions of the two parents are one half, of the grandparents one sixteenth. Exceptional characteristics, such as the artistic faculty, are the result of fortuitous ancestral heritages, and the chances are five to one against such faculty being transmitted in full force. The more rare a genius is, the greater are the chances of his not begetting a son as richly endowed as himself; for the law of regression to mediocrity tells heavily against it. This law Galton has demonstrated with great fullness; it is the factor of stability which causes all exceptional variations to gravitate back to the common race type.

Galton’s researches, taken altogether, certainly support Weismann’s central idea of heredity. First, considering their entirely independent and diverse lines of research, the coincidence between their general conclusions lends strong presumption in favor of their views; and, second, they support the theory of continuity of the race plasma as the only one which will explain the main laws of inheritance, rendering it almost certain that Weismann is on the right track so far as the physical process of heredity is concerned, although it is still an open question whether this plasma is as isolated from the body plasma as he supposes it. In what follows, therefore, I am not to be understood as opposing the continuity idea, but rather that of the isolation of the plasma, which, it is clear, is wholly at variance with Lamarck’s principle ; and I think it can be shown that Galton’s laws of regression and race stability furnish very powerful arguments against Weismann’s views of evolution by unaided selection.

Now let us consider how Weismann disposes of some of the more familiar arguments for the inheritance of acquired faculties. One of the first which suggests itself is, that high mental development in certain families and races is in part the product of the continual exercise of the faculties of the mind; that the prominent rôle which the brain plays in the life of civilized man has resulted in the higher nervous organization which distinguishes the European from the savage; in other words, that talents represent in some degree the “ summation of the skill attained by exercise in the course of each individual life.” Weismann rightly considers talents in the individual as the happy combination of exceptionally high gifts developed in one special direction, probably from the crossing of the mental dispositions of the parents, so beautifully expressed by Goethe : —

The reason, be argues, why they appear more highly developed at certain periods is, that this ever-shifting civilization of ours puts a premium upon, and thus favors, the survival of the special talent which is best adapted to the times. “ How many poets arose in Germany during the period of sentiment which marked the close of the last century, and how completely all poetic gifts seemed to have disappeared during the Thirty Years’ War! ” There is absolutely no trustworthy proof, he says, that talents have been improved by exercise in any particular series of generations. The Bach family shows that musical talent can be transmitted from generation to generation ; but the high-water mark in this family lies in the middle, and not at the end, of the series of generations, as it should do if the results of musical practice are transmitted.

This mode of explanation certainly is plausible, and can be applied with the full force which we always concede to the natural selection argument where the character is of sufficient importance materially to affect the animal in its struggle for existence. Therefore let us examine another bodily character in which selection can take no part, namely, short-sightedness. This is certainly hereditary, and the general deduction has been that in countries such as Germany, where it is increasing so rapidly as to have become almost a race characteristic, each generation has developed a slightly further degree of the affection by misuse of the eyes, causing it to accumulate. Weismann meets this apparently indisputable example of the transmission of an acquired character by a twofold reply. He first suggests that the progenitor of one of these generations may have had a congenital disposition to myopia, and have developed weak sight from an original predisposition, which he naturally transmitted, not as an acquired character. Secondly, eyesight in the European is no longer under the preserving influence of selection, as in the savage state, where it is of great value in war and in the chase. A shortsighted savage is at a decided disadvantage, while a German similarly affected provides himself with spectacles, and is the equal of any.

The latter example shows how Weismann’s followers are put on the defensive, when they try to explain the introduction of a new character without the Lamarckian principle, and solely by ingenious application of the Darwinian principle. They are forced to exalt the latter, and, as Poulton says, are directing their researches in every line “ inspired by one firm purpose, — the desire to support and illustrate by new examples the preëminent principle which we owe to the life and writings of Charles Darwin.” The modern theory has thus become a far more complex affair than its author foresaw. Evolution includes three processes — development, balance, or poise, in which organs remain in statu quo, and degeneration — which these NeoDarwinians, as they are dubbed by their opponents, must account for. They explain development by direct selection of favorable variations ; balance by the sustaining power of selection ; degeneration by Panmixia, or cessation of selection, an independent discovery of Romanes and Weismann ; or even by the reversal of selection, for where an organ becomes useless it is of absolute disadvantage to the individual, since it is consuming forces which might better go to some useful part. These elaborations of Darwin’s law rest upon the assumption, difficult of proof, that all organs in process of evolution play their part in fitness to survive, and must face all the numerous theoretical objections which have been ably advanced against the original theory, as well as the fact that Darwin himself lost faith in its universal application.

The opponents of the Neo-Darwinian school are as strong in the explanations which they can offer of many of the more complex phenomena of evolution as they are weak when they endeavor to complete their system by some intelligible principle of heredity ; and it is only fair to Weismann to mention that at the outset he accepted the Lamarckian principle, and has not attacked it per se, but simply because, from the heredity standpoint, it is to him inconceivable. Of modern Englishmen, I believe Herbert Spencer stands nearest Darwin’s maturer views, although reacting against the exclusive selection theory a little further than Darwin lived to do. “ Nowadays,” he writes, “ most naturalists are more Darwinian than Darwin himself.... I mean that the particular factor which he first recognized as having played so immense a part in organic evolution has come to be regarded as the sole factor, though it was not so regarded by him. Of this reaction displayed in the later writings of Mr. Darwin let us now ask, Has it not to be carried further ? ”

Spencer would attribute to selection most protective structures, the coloring of animals and plants, or such adaptations as the pitcher plant, the Venus flytrap, and such dermal structures as the porcupine quill, for in these cases we can see that each plus-variation would be directly beneficial. Selection also best explains the phenomena of mimicry. In the case of the reduction of the jaws in civilized races and in the domestic dog, we have, on the other hand, an instance where he believes the only conceivable cause is diminished use. Darwin has attributed the long neck of the giraffe to selection. Spencer admits that this may be the true explanation, but points out that the entire muscular, vascular, and skeletal structure of the giraffe is adjusted to carry this neck ; and there is no reason to suppose that all such adjustments would be properly correlated without inheritance of functionally produced modifications. This is called the argument from correlation, and is one of the strongest which can be brought against the selection theory. He advocates the older view as to the origin of special talents, which we have seen Weismann opposing.

As life grows complex, as a healthy life demands many powers, “ as fast as the number of bodily and mental faculties increases, and as fast as the maintenance of life comes to depend less on the amount of any one, and more on the combined action of all, so fast does the production of specialties of character by natural selection alone become difficult ; ” above all does it seem to be so with the species like man, and with such of the human powers as have minor shares in aiding the struggle for life, — the æsthetic faculties, for example.

“ How comes there that endowment of musical faculty which characterizes modern Europeans at large as compared with their remote ancestors ? ... It is not evident that an individual savage, who had a little more musical perception than the rest, would derive any such advantage in the maintenance of life as would secure the spread of his superiority by the inheritance of the variation. We cannot suppose that appreciation of harmony, which is relatively modern, can have arisen by descent from the men in whom successive generations increase the appreciation of it, the composers and musical performers. . . . Those who inherited their especial traits have not thereby been so aided in the struggle for existence as to further the spread of such traits.”

These passages are from Spencer’s recent essays, The Factors of Organic Evolution, which present altogether a forcible and logical argument for the inheritance of acquired characters. We can understand his earnestness in this discussion when we consider that his whole mechanical conception of living matter, his biological philosophy in short, is at stake in this issue. For if this principle is non-existent, his life work, both upon biology and psychology, is seen to rest wholly upon false premises.

In this country flourish the Neo-Lamarckians, most prominent and radical among whom is Professor Cope, who has worked out a complete system in his Origin of the Fittest. He assigns a subsidiary rôle to natural selection, believing it can originate nothing ; it only preserves, while the main factor in both development and degeneration and in the very inception of organs is the principle of Lamarck. Other able and ardent supporters of this revival of Lamarckism are Hyatt, Ryder, Dall, and Packard. The reader will observe the coincidence between opinions and geographical lines, which reminds us of the Indian fable of the elephant and the nine blind men, each of whom gave an entirely different description of the animal, according to the part of the body which he happened to examine; the point of the illustration being that, in looking over the whole field of writers, we find the advocates of these different views have been unconsciously guided by the classes of facts which are most obvious in their particular fields of research. All our countrymen have derived their bias chiefly from the palæontological series which are so richly suggestive of Lamarckian ideas, and afford a strong vantage ground. Long chapters in the rise and fall of organs, as, for example, in the ancient pedigree of the American horse, appear to furnish the most indisputable evidence of the inherited effects of use and disuse. Thus, the old familiar lines of the Lamarckian argument have been gone over, but with contributions of much that is original owing to these great advantages. As this is also my own special field, I may be pardoned for selecting an illustration from it.

I will show the bearing of this fossil evidence upon the laws of variation, variability being, whatever view we espouse, the essence of evolution. Old readers of the Atlantic Monthly will recall that Asa Gray was one of the first in this country to champion the cause of Darwin, — a support which is gracefully acknowledged in the Life and Letters. The exception he made to Darwin’s views (partly from his desire to substitute a progressive and continuous for the old fixed teleology), somewhat in common with Nägeli, the great German botanist, was that variations are not at random or in all directions, as they would be according to Darwin’s original notion, now revived by Weismann, but that they follow certain definite purposive lines of adaptation. Such a perfecting principle in variation, if observed in any part of the animal kingdom, would naturally apply throughout, and be of such immense importance that evidence concerning it should be sifted with the greatest care. The researches of Wagner, Semper, and Eimer strongly, if not conclusively, point this way among the invertebrates ; to the American school principally is due the credit of establishing it among the vertebrates. The distinctive feature of palæontological evidence is that, for example, in such a series as the fossil horses we cannot only follow the rise of useful structures back to their minute and apparently useless condition, but we are in even before their birth, so to speak. What is the result ? Do we find Dame Nature trying on a dozen caps, and selecting the one which fits ? Not at all. The new part arises precisely where it is wanted, and slowly, through an entire geological sub-period perhaps, develops into a stage of usefulness. We see with Weismann and Galton the element of chance; but the dice appear to be loaded, and in the long run turn “ sixes ” up. Now enters the question, What loads the dice ?

A somewhat exaggerated form of reply is found in the discovery that race adaptation follows the law of individual adaptation. Take the familiar example of the single toe of the horse ; and we now know vastly more about it than we did when Huxley, fresh from the Yale College Museum, delighted American audiences with the tale of the loss of the four lateral toes. This loss was far from the simple matter it at first seemed to be, for it appears from the researches of Kowalevsky, Cope, Ryder, and myself, with the aid of Muybridge’s instantaneous photographs of animal locomotion, that every time the foot rests upon the ground the strains cause infinitesimal alterations in all the bones of the leg; and during the early geological periods these strains were constantly changing pari passu with the gradual decrease of the lateral and increase of the central digits. This principle applies to the whole skeleton : the adult horse is a slightly more perfect machine than the young horse; this is what I mean by individual adaptation. So precisely, in every detail, does the course of evolution follow the course of individual adaptation that, endowing the eocene Hyracotherium with the age of Methuselah and a corresponding supply of elixir vitæ, we can readily imagine its transmutation into the miocene Mesohippus. Now, it is hard for us to believe, with the new school, that these invariable sequences of race adaptation upon individual adaptation are not instances of cause and effect. If they are, they afford absolute proof of the transmission of acquired characters. If they are not, then all our painstaking researches and vast literature on this subject are of no more value than waste paper, for they lead to no result.

To return to man, the human problem is as much more complex than that of the lower animals as the average human life is more complex and varied. Small wonder that Galton has reached such uncertain results. What two hours of the day or days of the year are we acting or thinking exactly alike? The German army drill, it is true, enforces a daily life to some degree approaching the mechanical routine of the quadruped ; but ordinarily this lasts but three years, so that the arguments which Weismann bases upon the non-inheritance of the Exercierknochen and other excrescences developed by handling the musket lose weight. Therefore we should not expect such inheritance as this except where a certain long-continued habit makes a deep impression upon the organism, and this habit is repeated in successive generations.

In conclusion, let us look again more closely to the bearing which the outcome of this discussion will have upon the conduct of life. If the Weismann idea triumphs, it will be in a sense a triumph of fatalism; for, according to it, while we may indefinitely improve the forces of our education and surroundings, and this civilizing nurture will improve the individuals of each generation, its actual effects will not be cumulative as regards the race itself, but only as regards the environment of the race; each new generation must start de novo, receiving no increment of the moral and intellectual advance made during the lifetime of its predecessors. It would follow that one deep, almost instinctive motive for a higher life would be removed if the race were only superficially benefited by its nurture, and the only possible channel of actual improvement were in the selection of the fittest chains of race plasma. Now, there can be no question that if the selection doctrine were so indelibly inscribed among our canons of life that we were seriously guided by it, consulting the family physician, lawyer, and clergyman in marriage selection, the race would improve far more rapidly than by the inheritance of the beneficial influences of nurture; for historic evolution teaches that such inheritance is at best very slow. This new knowledge would then be a distinct gain to humanity ; but would not its effects be more than offset by the inculcation of the twin principle of Weismann, that acquired characters are not inherited ? For, living by this, a man might in his own early life squander the entire capital of a fine intellectual and moral inheritance, and yet subsequently transmit it undiminished and unimpaired to his children, by what we might term a principle of entail in heredity.

Thus, this important question is as complex in the sphere of mind and morals as it is in the lower physical and animal sphere. One must candidly admit that the arguments upon both sides are so plausible that, listening alternately to each, one is reminded of the vacillation of the Roman mob when addressed by Brutus and Antony. An impartial opm ion as to the merits of the respective schools is that in the phenomena of evolution the Lamarckians have the best of the argument, while in the phenomena of simple heredity their opponents are strongest. It is evident that there can be no reconciliation ; it is absolute surrender on one side or the other, for no half-way position is tenable.

Huxley has aptly described the minds of naturalists as being in a state of ferment during the few years preceding the publication of the discovery of Darwin’s law ; for while many supported the “special creation hypothesis, there was an uneasy consciousness that all was not right. Such are exactly our present symptoms, and is it not possible that out of all this second ferment we shall discover some new factor of evolution, which will work as great a surprise and revolution in our ideas as did the theory of natural selection in 1858 ?

Henry Fairfield Osborn.