Appendix Ii:

ON TELEGONY.

A WIDELY different view, however, is taken by Mr. Herbert Spencer with regard to the theoretical interpretation of telegony. This, indeed, is precisely the opposite view to the one which is given in the text. For while I agree with Professor Weismann in holding that the facts of telegony (supposing them to be facts) are as compatible with the theory of germ-plasm as with that of gemmules, “physiological units,” or any other theory which postulates a centripetal flow of the carriers of heredity from somatic-cells to germ-cells, Mr. Spencer is of the opinion that these facts are destructive of any theory which postulates a continuity in the substance of heredity—i.e., a centrifugal flow of the carriers of heredity. And, unquestionably, Mr. Spencer’s view is the prevalent one. Therefore, seeing that his opinion is not only of weight per se, but is shared by the scientific world in general, I will here transcribe a somewhat lengthy discussion which I have recently held with him upon the subject.

In the Contemporary Review for March, Mr. Spencer wrote as follows:—

We pass now to evidence not much known in the world at large, but widely known in the biological world, though known in so incomplete a manner as to be undervalued in it. Indeed, when I name it probably many will vent a mental pooh-pooh. The fact to which I refer is one of which record is preserved in the museum of the College of Surgeons, in the shape of paintings of a foal borne by a mare not quite thoroughbred, to a sire which was thoroughbred—a foal which bears the markings of the quagga. The history of this remarkable foal is given by the Earl of Morton, F.R.S., in a letter to the President of the Royal Society (read November 23, 1820). In it he states that wishing to domesticate the quagga, and having obtained a male, but not a female, he made an experiment.

I tried to breed from the male quagga and a young chestnut mare of seven-eighths Arabian blood, and which had never been bred from; the result was the production of a female hybrid, now five years old, and bearing, both in her form and in her colour, very decided indications of her mixed origin. I subsequently parted with the seven-eighths Arabian mare to Sir Gore Ouseley, who has bred from her by a very fine black Arabian horse. I yesterday morning examined the produce, namely, a two-year-old filly and a year-old colt. They have the character of the Arabian breed as decidedly as can be expected, where fifteen-sixteenths of the blood are Arabian; and they are fine specimens of that breed; but both in their colour and in the hair of their manes they have a striking resemblance to the quagga. Their colour is bay, marked more or less like the quagga in a darker tint. Both are distinguished by the dark line along the ridge of the back, the dark stripes across the fore-hand, and the dark bars across the back part of the legs.

Lord Morton then names sundry further correspondences. Dr. Wollaston, at that time President of the Royal Society, who had seen the animals, testified to the correctness of his description, and, as shown by his remarks, entertained no doubt about the alleged facts. But good reason for doubt may be assigned. There naturally arises the question—How does it happen that parallel results are not observed in other cases? If in any progeny certain traits not belonging to the sire, but belonging to a sire of preceding progeny, are reproduced, how is it that such anomalously-inherited traits are not observed in domestic animals, and indeed in mankind? How is it that the children of a widow by a second husband do not bear traceable resemblances of the first husband? To these questions nothing like satisfactory replies seem forthcoming; and, in the absence of replies, scepticism, if not disbelief, may be held reasonable.

There is an explanation, however. Forty years ago I made acquaintance with a fact which impressed me by its significant implications; and has, for this reason I suppose, remained in my memory. It is set forth in the Journal of the Royal Agricultural Society, vol. xiv. (1853), pp. 214 et seq., and concerns certain results of crossing English and French breeds of sheep. The writer of the translated paper, M. Malingié-Nouel, Director of the Agricultural School of La Charmoise, states that when the French breeds of sheep (in which were included “the mongrel Merinos”) were crossed with an English breed, “the lambs present the following results. Most of them resemble the mother more than the father; some show no trace of the father.” Joining the admission respecting the mongrels with the facts subsequently stated, it is tolerably clear that the cases in which the lambs bore no traces of the father were cases in which the mother was of pure breed. Speaking of the results of these crossings in the second generation “having seventy-five per cent. of English blood,” M. Nouel says:—“The lambs thrive, wear a beautiful appearance, and complete the joy of the breeder.... No sooner are the lambs weaned than their strength, their vigour, and their beauty begin to decay.... At last the constitution gives way ... he remains stunted for life”: the constitution being thus proved unstable or unadapted to the requirements. How, then, did M. Nouel succeed in obtaining a desirable combination of a fine English breed with the relatively poor French breeds?

He took an animal from “flocks originally sprung from a mixture of the two distinct races that are established in these two provinces [Berry and La Sologne],” and these he “united with animals of another mixed breed, ... which blended the Tourangelle and native Merino blood of” La Beauce and Touraine, and obtained a mixture of all four races “without decided character, without fixity, ... but possessing the advantage of being used to our climate and management.”

Putting one of these “mixed-blood ewes to a pure New-Kent ram ... one obtains a lamb containing fifty-hundredths of the purest and most ancient English blood, with twelve and a-half hundredths of four different French races, which are individually lost in the preponderance of English blood, and disappear almost entirely, leaving the improving type in the ascendant.... All the lambs produced strikingly resembled each other, and even Englishmen took them for animals of their own country.”

M. Nouel goes on to remark that when this derived breed was bred with itself, the marks of the French breeds were lost. “Some slight traces could be detected by experts, but these soon disappeared.”

Thus we get proof that relatively pure constitutions predominate in progeny over much mixed constitutions. The reason is not difficult to see. Every organism tends to become adapted to its conditions of life; and all the structures of a species, accustomed through multitudinous generations to the climate, food, and various influences of its locality, are moulded into harmonious co-operation favourable to life in that locality: the result being that in the development of each young individual, the tendencies conspire to produce the fit organization. It is otherwise when the species is removed to a habitat of different character, or when it is of mixed breed. In the one case its organs, partially out of harmony with the requirements of its new life, become partially out of harmony with one another; since, while one influence, say of climate, is but little changed, another influence, say of food, is much changed; and, consequently, the perturbed relations of the organs interfere with their original stable equilibrium. Still more in the other case is there a disturbance of equilibrium. In a mongrel the constitution derived from each source repeats itself as far as possible. Hence a conflict of tendencies to evolve two structures more or less unlike. The tendencies do not harmoniously conspire; but produce partially incongruous sets of organs. And evidently where the breed is one in which there are united the traits of various lines of ancestry, there results an organization so full of small incongruities of structure and action, that it has a much-diminished power of maintaining its balance; and while it cannot withstand so well adverse influences, it cannot so well hold its own in the offspring. Concerning parents of pure and mixed breeds respectively, severally tending to reproduce their own structures in progeny, we may therefore say, figuratively, that the house divided against itself cannot withstand the house of which the members are in concord.

Now if this is shown to be the case with breeds the purest of which have been adapted to their habitats and modes of life during some few hundred years only, what shall we say when the question is of a breed which has had a constant mode of life in the same locality for ten thousand years or more, like the quagga? In this the stability of constitution must be such as no domestic animal can approach. Relatively stable as may have been the constitutions of Lord Morton’s horses, as compared with the constitutions of ordinary horses, yet, since Arab horses, even in their native country, have probably in the course of successive conquests and migrations of tribes become more or less mixed, and since they have been subject to the conditions of domestic life, differing much from the conditions of their original wild life, and since the English breed has undergone the perturbing effects of change from the climate and food of the East to the climate and food of the West, the organizations of the horse and mare in question could have had nothing like that perfect balance produced in the quagga by a hundred centuries of harmonious co-operation. Hence the result. And hence at the same time the interpretation of the fact that analogous phenomena are not perceived among domestic animals, or among ourselves; since both have relatively mixed, and generally extremely mixed, constitutions, which, as we see in ourselves, have been made generation after generation, not by the formation of a mean between two parents, but by the jumbling of traits of the one with traits of the other, until there exist no such conspiring tendencies among the parts as cause repetition of combined details of structure in posterity.

Expectation that scepticism might be felt respecting this alleged anomaly presented by the quagga-marked foal, had led me to think over the matter; and I had reached this interpretation before sending to the College of Surgeons Museum (being unable to go myself) to obtain the particulars and refer to the records. When there was brought to me a copy of the account as set forth in the “Philosophical Transactions,” it was joined with the information that there existed an appended account of pigs, in which a parallel fact had been observed. To my immediate inquiry—“Was the male a wild pig?”—there came the reply: “I did not observe.” Of course I forthwith obtained the volume, and there found what I expected. It was contained in a paper communicated by Dr. Wollaston from Daniel Giles, Esq., concerning his “sow and her produce,” which said that

she was one of a well-known black and white breed of Mr. Western, the Member for Essex. About ten years since I put her to a boar of the wild breed, and of a deep chestnut colour, which I had just received from Hatfield House, and which was soon afterwards drowned by accident. The pigs produced (which were her first litter) partook in appearance of both boar and sow, but in some the chestnut colour of the boar strongly prevailed.

The sow was afterwards put to a boar of Mr. Western’s breed (the wild boar having been long dead). The produce was a litter of pigs some of which, we observed with much surprise, to be stained and clearly marked with the chestnut colour which had prevailed in the former litter.

Mr. Giles adds that in a second litter of pigs, the father of which was of Mr. Western’s breed, he and his bailiff believe there was a recurrence, in some, of the chestnut colour, but admits that their “recollection is much less perfect than I wish it to be.” He also adds that, in the course of many years’ experience, he had never known the least appearance of the chestnut colour in Mr. Western’s breed.

What are the probabilities that these two anomalous results should have arisen, under these exceptional conditions, as a matter of chance? Evidently the probabilities against such a coincidence are enormous. The testimony is in both cases so good that, even apart from the coincidence, it would be unreasonable to reject it; but the coincidence makes acceptance of it imperative. There is mutual verification, at the same time that there is a joint interpretation yielded of the strange phenomenon, and of its non-occurrence under ordinary circumstances.

And now, in the presence of these facts, what are we to say? Simply that they are fatal to Weismann’s hypothesis. They show that there is none of the alleged independence of the reproductive cells; but that the two sets of cells are in close communion. They prove that while the reproductive cells multiply and arrange themselves during the evolution of the embryo, some of their germ-plasm passes into the mass of somatic-cells constituting the parental body, and becomes a permanent component of it. Further, they necessitate the inference that this introduced germ-plasm, everywhere diffused, is some of it included in the reproductive cells, subsequently formed. And if we thus get a demonstration that the somewhat different units of a foreign germ-plasm permeating the organism, permeate also the subsequently-formed reproductive cells, and affect the structures of the individuals arising from them, the implication is that the like happens with those native units which have been made somewhat different by modified functions: there must be a tendency to inheritance of acquired characters.

My reply to this appeared in the April issue of the Contemporary Review, as follows:—

Influence on Progeny of a Previous Sire.

This is the last of the arguments which Mr. Spencer advances against the position of Professor Weismann. Alluding to the case of Lord Morton’s mare, he represents that the phenomenon which it serves so well to illustrate—viz., the influence of a previous sire on the progeny of another by the same dam—is hopelessly at variance with the theory of germ-plasm. I cannot quite gather the explanation which he would give of this phenomenon, further than that in some way or another it betokens an immediate influence of the hereditary material of the male on the body-tissues (“somatic cells”) of the female. And this is the view which is taken of the phenomenon by the Lamarckians in general. Yet, if we consider all that such an explanation involves, we shall find that it is a highly complex explanation, for it involves the following chain of hypotheses:—The first impregnation affects many, if not all, the somatic tissues of the mother by the germinal matter of the father; these tissues, in their turn, react on the maturing ova; this action and reaction is such that when one of the ova is afterwards fertilized by a different sire, the resulting offspring more or less resemble the preceding sire. Unfortunately, neither Weismann himself nor any of his followers, as far as I know, has hitherto published an opinion on the subject; but I imagine that his answer would be three-fold. First, he may question the fact. Secondly, even admitting the fact, he may say it is much more easy to explain it by supposing that the germ-plasm of the first sire has in some way or another become partly commingled with that of the immature ova, as well as with that of the mature one which it actually fertilizes; and, if so, it would naturally assert its influence on the progeny of a subsequent sire. Millions of spermatozoa must have been playing around the ovaries after the first copulation, and only one of them was needed to fertilize the mature ovum. It is not necessary to suppose that some of the others succeeded in penetrating any of the immature ova, while these were still embedded in the substance of their ovaries. It may be that the life of “ids” Is not commensurate with that of their containing spermatozoa. After the latter have perished and disintegrated, their ids may escape in thousands of millions, bathing in a dormant state the whole surfaces of both ovaries. And, if so, it is conceivable that when subsequent ova mature—i.e., come to the surface of their ovaries and rupture their follicles—these dormant ids adhere to their porous walls, through which they may pass. This may not seem a very probable explanation; but, at any rate, it is a less improbable one than that on which the Neo-Lamarckians would found an argument against the continuity of germ-plasm. For,—

Thirdly, is it not literally inconceivable that this Neo-Lamarckian explanation can be the true one? Can it be seriously contemplated that there is any such mechanism as the explanation must needs assume? If it is difficult to accept such a machinery as is supposed by the theory of pangenesis, whereby every cell in the body casts off “gemmules,” which are the carriers of heredity from their respective tissues to the germinal elements, what are we to say of such a machinery as the following:—A machinery which distributes through the body of a female gemmules from the disintegrated spermatozoa of her mate; which distributes them selectively, so that they shall all eventually lodge in those tissue-cells of the female which correspond, part for part, with the tissue-cells of the male from which they were originally derived; which then insures that when a gemmule has thus reached its appropriate cell in the female body, it will thereupon modify the pre-existing gemmules in that cell, so that when they are shed and go to form the germinal contents of future ova, they endow the latter with the hereditary qualities of the male in question?

Such, it seems to me, is a fair statement of the whole case up to date. But I think it may be apposite now to publish the main results of an inquiry on which I have been engaged for the last three years.

First as to the facts. The investigations have been pursued on three different lines: (1) I raised discussions on the subject in the principal breeders’ and fanciers’ journals of this country, and also of America. (2) I entered into private correspondence with contributors of the largest experience, and also with professional and amateur breeders, fanciers, &c., who addressed me directly on the subject. (3) I started experiments with the varieties which these inquiries indicated as most likely to yield positive results. At present nothing need be said with regard to these experiments, because they are not sufficiently matured. But it is desirable to state the general upshot of the correspondence.

The principal result is to show that the phenomenon is of much less frequent occurrence than is generally supposed. Indeed, it is so rare that I doubt whether it takes place in more than one or two per cent. of cases. I must add, however, that nearly all my professional correspondents would deem this an absurdly low estimate. Most of them are quite persuaded that it is of frequent occurrence, many of them regard it as a general rule, while some of them go so far as to make a point of always putting a mare, a bitch, &c. to a good pedigree male in her first season, so that her subsequent progenies may be benefited by his influence, even though they be engendered by inferior sires. But I am certain that these estimates must be largely discounted in view of merely accidental resemblances, and still more on account of the prevalent belief upon the subject, which, where unquestioningly entertained, prevents anything like a critical estimate being formed.

But that the phenomenon does occur in some small percentage of cases there can be no reasonable doubt—as a result, I mean, of analysing the hundreds of cases which have now been submitted to me, especially with regard to dogs. One thoroughly well observed case occurring among pedigree animals is worth any number of slipshod statements, when precedent belief, inefficient isolation, exaggeration of memory, and so forth, have to be allowed for. On the present occasion space does not admit of giving such special instances, so I must ask it to be taken for granted that my evidence is enough to prove the fact of a previous sire asserting his influence on a subsequent progeny, although this fact is one of comparatively rare occurrence. It may be added that I have failed to find any good evidence of its ever occurring at all in the case of man. For although I have met with an alleged instance of a white woman, who, after having borne children to a negro husband, had a second family to a white one, in which some negro characteristics appeared, I have not been able to meet with any corroboration of this instance. I have made inquiries among medical men in the Southern States of America, where in the days of slavery it was frequently the custom that young negresses should bear their first children to their masters, and their subsequent children to negro husbands; but it never seems to have been observed, according to my correspondents, that these subsequent children were other than pure negroes. Such, however, was not the same case as the one above mentioned, but a reciprocal case; and this may have made a difference. If any reader should happen to know of another instance where a negro was the first husband, I hope he will inform me as to the result.

It has hitherto puzzled me why the phenomenon in question, since it does certainly occur in some cases, should occur so rarely as the above inquiries prove. But I think that Mr. Spencer’s suggestion on this point is a valuable one, as it seems to present an excellent promise of solving the puzzle.

This suggestion, it will be remembered, is that when the first sire is of a relatively stable and also of a markedly different ancestral stock from the dam—e.g., of a different species, as in the case of Lord Morton’s mare—there will be most likelihood of his impressing his ancestral characters on the progeny of the second sire. And, as he remarks, it would indeed be an extraordinary coincidence if both the well-authenticated cases given in the College of Surgeons Catalogue should have conformed to his explanation by mere accident. To which I may add that the supposition of such an accidental coincidence would seem to be virtually excluded by the recent occurrence of yet a third case of exactly the same kind. This took place in the Zoological Gardens, where a wild ass of one species was the previous sire to a foal born of another species: the subsequent sire was of the same species as the mother, and his foal, born a few months ago, presented an unmistakable resemblance to the other species. A brief account of the particulars is given by Mr. Tegetmeier in the Field for December 14, 1892.

So much, then, for the facts. As regards their interpretation, it certainly seems to me that the one which I have supposed to be given by Weismann is less difficult of acceptance than the one which is given by the Lamarckians, as we have seen above. But it also seems to me that the latter explanation is not the only one available under the Lamarckian hypothesis. For, even under this hypothesis, there is no need to assume that the influence of the first sire is exerted on all the somatic tissues of the mother, and that these again reflect this influence on the ovum which is afterwards fertilized by the second sire. A mechanism that could effect all this may well be deemed impossible. But a much simpler explanation can be furnished by the Neo-Lamarckians, on lines similar to those upon which I have supposed that Weismann’s explanation would run. For, on their common supposition that the substance of heredity is particulate, it matters not in the present connexion whether we suppose the particles to be ids or gemmules. Indeed, it is more in accordance with the hypothetical endowments of the latter than of the former, that they should be capable of penetrating the coats of an ovum, if they can survive the disintegration of their containing spermatozoön. Nevertheless, thus far it does not seem to me that any theory belonging to the family of pangenesis can gain any advantage over the theory of germ-plasm, by appealing to the fact of a previous sire sometimes affecting the progeny of a subsequent one. The case, however, is widely different if we turn from animals to plants, thus.

The advantage which any theory of gemmules seeks to gain over the theory of germ-plasm by an appeal to the fact in question, consists in supposing that the influence of the previous sire is exercised in the first instance on the somatic cells of the female. For this would prove that the germinal elements of the male are capable of communicating their hereditary qualities, not only by mixing with the germinal elements of the female (as in ordinary fertilization) but also by direct contact with the general tissues of the female. And this again would prove that the fundamental postulate of the theory of germ-plasm is erroneous—i.e., the postulate of the continuity of germ-plasm, or of its perpetual restriction to a “sphere” of its own. This, as all who are acquainted with the literature of the subject will at once perceive, would be a serious blow to the whole Weismannian system. But, as we have seen, the current Lamarckian interpretation of the fact in question involves the supposition of a physiological machinery so inconceivably complex that instead of serving to corroborate the theory of gemmules (or of physiological units) it would go to render that theory incredible.

If, however, we turn to plants, we find a considerable number of facts which unquestionably demonstrate the only point which this interpretation has been adduced to suggest. For these facts show that, in not a few cases, the germinal matter of pollen-grains is capable of asserting its influence beyond the ovules to the somatic tissues of the ovary, and even to the flower-stalk of the mother plant. Here, then, we have simple and conclusive evidence of the material of heredity exercising a direct influence on somatic tissues. How this well-known fact is to be met by the theory of germ-plasm is a question which does not seem to have thus far engaged the attention of Professor Weismann, or of any of his followers. For particulars touching this phenomenon, so highly important in its relation to the theory of germ-plasm, I cannot do better than refer to the eleventh chapter of Darwin’s work on the “Variation of Animals and Plants under Domestication.”

Again, in the Contemporary Review for May, Mr. Spencer wrote:—

In the essay to which this is a postscript, conclusions were drawn from the remarkable case of the horse and quagga there narrated, along with an analogous case observed among pigs. These conclusions have since been confirmed. I am much indebted to a distinguished correspondent who has drawn my attention to verifying facts furnished by the offspring of whites and negroes in the United States. Referring to information given him many years ago, he says:—“It was to the effect that the children of white women by a white father had been repeatedly observed to show traces of black blood, in cases when the woman had previous connexion with [i. e., a child by] a negro.” At the time I received this information, an American was visiting me; and, on being appealed to, answered that in the United States there was an established belief to this effect. Not wishing, however, to depend upon hearsay, I at once wrote to America to make inquiries. Professor Cope of Philadelphia has written to friends in the South, but has not yet sent me the results. Professor Marsh, the distinguished palæontologist, of Yale, New Haven, who is also collecting evidence, sends a preliminary letter in which he says:—“I do not myself know of such a case, but have heard many statements that make their existence probable. One instance, in Connecticut, is vouched for so strongly by an acquaintance of mine, that I have good reason to believe it to be authentic.”

That cases of the kind should not be frequently seen in the North, especially nowadays, is of course to be expected. The first of the above quotations refers to facts observed in the South during slavery days; and, even then, the implied conditions were naturally very infrequent. Dr. W. J. Youmans of New York has, on my behalf, interviewed several medical professors, who, though they have not themselves met with instances, say that the alleged result, described above, “is generally accepted as a fact.” But he gives me what I think must be regarded as authoritative testimony. It is a quotation from the standard work of Professor Austin Flint, and runs as follows:—

A peculiar and, it seems to me, an inexplicable fact is, that previous pregnancies have an influence upon offspring. This is well known to breeders of animals. If pine-blooded mares or bitches have been once covered by an inferior male, in subsequent fecundations the young are likely to partake of the character of the first male, even if they be afterwards bred with males of unimpeachable pedigree. What the mechanism of the influence of the first conception is, it is impossible to say; but the fact is incontestable. The same influence is observed in the human subject. A woman may have, by a second husband, children who resemble a former husband, and this is particularly well marked in certain instances by the colour of the hair and eyes. A white woman who has had children by a negro may subsequently bear children to a white man, these children presenting some of the unmistakable peculiarities of the negro race.

Dr. Youmans called on Professor Flint, who remembered “investigating the subject at the time his larger work was written [the above is from an abridgment], and said that he had never heard the statement questioned.”

Some days before I received this letter and its contained quotation, the remembrance of a remark I heard many years ago concerning dogs, led to the inquiry whether they furnished analogous evidence. It occurred to me that a friend who is frequently appointed judge of animals at agricultural shows, Mr. Fookes, of Fairfield, Pewsey, Wiltshire, might know something about the matter. A letter to him brought various confirmatory statements. From one “who had bred dogs for many years” he learnt that—

It is a well-known and admitted fact that if a bitch has two litters by two different dogs, the character of the first father is sure to be perpetuated in any litters she may afterwards have, no matter how pure-bred a dog may be the begetter.

After citing this testimony, Mr. Fookes goes on to give illustrations known to himself.

A friend of mine near this had a very valuable Dachshund bitch, which most unfortunately had a litter by a stray sheep-dog. The next year her owner sent her on a visit to a pure Dachshund dog, but the produce took quite as much of the first father as the second, and the next year he sent her to another Dachshund with the same result. Another case:—A friend of mine in Devizes had a litter of puppies, unsought for, by a setter from a favourite pointer bitch, and after this she never bred any true pointers, no matter of what the paternity was.

These further evidences, to which Mr. Fookes has since added others, render the general conclusion incontestable. Coming from remote places, from those who have no theory to support, and who are some of them astonished by the unexpected phenomena, the agreement dissipates all doubt. In four kinds of mammals, widely divergent in their natures—man, horse, dog, and pig—we have this same seemingly anomalous kind of heredity made visible under analogous conditions. We must take it as a demonstrated fact that, during gestation, traits of constitution inherited from the father produce effects upon the constitution of the mother; and that these communicated effects are transmitted by her to subsequent offspring. We are supplied with an absolute disproof of Professor Weismann’s doctrine that the reproductive cells are independent of, and uninfluenced by, the somatic cells; and there disappears absolutely the alleged obstacle to the transmission of acquired characters....

There is one other passage in Dr. Romanes’ criticism—that concerning the influence of a previous sire on progeny—which calls for comment. He sets down what he supposes Weismann will say in response to my argument. “First, he may question the fact.” Well, after the additional evidence given above, I think he is not likely to do that; unless, indeed, it be that along with readiness to base conclusions on things “it is easy to imagine” there goes reluctance to accept testimony which it is difficult to doubt. Second, he is supposed to reply that “the germ-plasm of the first sire has in some way or another become partly commingled with that of the immature ova”; and Dr. Romanes goes on to describe how there may be millions of spermatozoa and “thousands of millions” of their contained “ids” around the ovaries, to which these secondary effects are due. But, on the one hand, he does not explain why in such case each subsequent ovum, as it becomes matured, is not fertilized by the sperm-cells present, or their contained germ-plasm, rendering all subsequent fecundations needless; and, on the other hand, he does not explain why, if this does not happen, the potency of this remaining germ-plasm is nevertheless such as to affect not only the next succeeding offspring, but all subsequent offspring. The irreconcilability of these two implications would, I think, sufficiently dispose of the supposition, even had we not daily multitudinous proof that the surface of a mammalian ovarium is not a sperm-atheca. The third difficulty Dr. Romanes urges is the inconceivability of the process by which the germ-plasm of a preceding male parent affects the constitution of the female and her subsequent offspring. In response, I have to ask why he piles up a mountain of difficulties based on the assumption that Mr. Darwin’s explanation of heredity by “Pangenesis” is the only available explanation preceding that of Weismann? and why he presents these difficulties to me more especially, deliberately ignoring my own hypothesis of physiological units? It cannot be that he is ignorant of this hypothesis, since the work in which it is variously set forth (“Principles of Biology,” §§ 66-97) is one with which he is well acquainted: witness his “Scientific Evidences of Organic Evolution”; and he has had recent reminders of it in Weismann’s “Germ-plasm,” where it is repeatedly referred to. Why, then, does he assume that I abandon my own hypothesis and adopt that of Darwin, thereby entangling myself in difficulties which my own hypothesis avoids? If, as I have argued, the germ-plasm consists of substantially similar units (having only those minute differences expressive of individual and ancestral differences of structure), none of the complicated requirements which Dr. Romanes emphasises exists, and the alleged inconceivability disappears.

To this I responded, in the Contemporary Review for June:—

With regard to the influence of a previous sire, I ventured in my article to show that, even supposing it to be a fact, the phenomena concerned would not constitute any valid evidence against Weismann’s theory of germ-plasm, and, of course, still less would “they prove that while the reproductive cells multiply and arrange themselves during the evolution of the embryo, some of their germ-plasm passes into the mass of somatic cells constituting the parental body, and becomes a permanent component of it,” with the result that the phenomena in question “are simply fatal to Weismann’s hypothesis.” For a much simpler and more probable explanation is to be found in supposing that the unused germ-plasm of the first sire may survive the disintegration of its containing spermatozoa in the Fallopian tubes of the female, and thus gain access to the hitherto unripe ova directly, instead of first having to affect the whole maternal organism, and then being reflected from it to them. I showed, at some length, how immensely complex the mechanism of any such process would necessarily have to be; and for the purposes of exposition I employed the terminology of Darwin’s theory of Pangenesis. Mr. Spencer now says: “In response, I have to ask why he piles up a mountain of difficulties based on the assumption that Mr. Darwin’s explanation of heredity by ‘Pangenesis’ is the only available explanation preceding that of Weismann? and why he presents these difficulties to me more expecially, deliberately ignoring my own hypothesis of physiological units?” Now my answer to this is very simple. I do not hold a brief for Weismann. On the contrary, I am in large measure an opponent of his views; and my only object in publishing my previous article was to save the theory of use-inheritance from what seemed to me the weaker parts of Mr. Spencer’s advocacy, while thus all the more emphasizing my acceptance of its stronger parts. Therefore, the impression which he seems to have gained from my attempts at impartiality is entirely erroneous. Far from “deliberately ignoring” any of his arguments or hypotheses which seemed to me at all available on the side of use-inheritance, I everywhere endeavoured to make the most of them. And, as regards this particular instance, I expressly used the term “gemmules,” instead of “physiological units,” simply because I could not see that, as far as my “mountain of difficulties” was concerned, it could make one atom of difference which term I employed. It now appears, however, that, in Mr. Spencer’s opinion, there is some very great difference. For, while he allows that the “mountain of difficulties” which I have “piled up” against his interpretation of the alleged phenomena would be valid on the supposition that the ultimate carriers of heredity are “gemmules,” he denies that such is the case if we suppose these ultimate carriers to be “physiological units.” For this statement, however, he gives no justification; and, as I am unable to conceive wherein the difference lies, I sincerely hope that in any subsequent editions of his pamphlet Mr. Spencer will furnish the requisite explanation. Gladly substituting the words “physiological units” wherever I have used the word “gemmules,” I am genuinely anxious to ascertain how he would overcome the “mountain of difficulties” in question. For I do not regard the subject as one of mere dialectics. It is a subject of no small importance to the general issue, Weismann versus Lamarck; and, therefore, if Mr. Spencer could show that the phenomena in question make exclusively in favour of the latter, as he alleges, he might profitably inform us in what way he supposes them to do so.

In conclusion, I would like to take this opportunity of explaining that my former article was written in Madeira, where I did not receive a copy of Weismann’s most recent work, entitled The Germ-plasm, until the Contemporary Review for April was being printed off. Thus, I was not then aware that in this work Professor Weismann had fully anticipated several of Mr. Spencer’s criticisms—including this matter of the influence of a previous sire. Here he adopts exactly the position which in my article I surmised that he would; so that, to all who have read The Germ-plasm, it must have appeared that I was prophesying after the event. Hence the need of this explanation.

Lastly, in the same issue of the Contemporary Review, Mr. Spencer explained:—

Mr. Darwin’s hypothesis of Pangenesis implies not only that the reproductive cell must contain numerous kinds of gemmules derived from different organs, but that the numbers of these gemmules must bear to one another something like the proportions which the originating organs bear to one another in size. The conception involves many different kinds, whose numbers are in many different proportions, and I supposed the difficulty alleged was, that for the influence of a previous sire to be communicated from the growing ftus to the mother would imply not only the transfer of the various kinds of gemmules derived from him, but also maintenance of their numerical proportions, and that again these gemmules, diffused throughout the maternal system, would have to be transferred in these proportions to the subsequently formed ova. No such difficulties arise if the units conveying hereditary characters are of one kind only.

From this it is apparent that Mr. Spencer has misunderstood “the difficulty alleged,” and that the desired explanation is not yet forthcoming. I did not say anything about “kinds” or “proportions” of the carriers of heredity; my difficulty is to conceive of any mechanism whereby these carriers can first directly influence the somatic-cells of the mother, and then indirectly reflect this influence upon her germ-cells. Also, I cannot see any obvious necessity for the intervention of the “embryo” in the process.

GLOSSARY.

=Acquired characters.=—See Somatogenetic characters.

=Amphigony= (=Häckel=).—Sexual reproduction.

=Amphimixis= (=Weismann=).—The mingling of the hereditary substances of two individuals in an act of sexual union.

=Ancestral germ-plasm.=—See p. 123.

=Asexual Reproduction.=—In which there is no liberation of special germ cells containing the potentiality of the adult organism, but in which the same object is effected by the liberation of buds, overgrowths, &c., which develop into the parent form. There are many forms of a-sexual reproduction.

=Atavism.=—The abnormal occurrence in existing species of characters which were peculiar to ancestral species, e.g., see Darwin and after Darwin, 2nd ed., Part I, p. 94.

=Biophore.=—See p. 123.

=Blastogenetic characters.=—See Plasmogenetic characters.

=Calyx.=—The outermost covering of the flower, which protects it before opening. Its position and precise function vary.

=Cell nucleus.=—A spherical or ovoid body embedded in the cell protoplasm, which has important functions in cell division and in reproduction. It consists of chromatin and achromatin. There are often several nuclei in one cell, whilst some cells have not been shown to have a nucleus at all.

=Cessation of Selection= (=Romanes=).—See Panmixia.

=Chromatin threads.=—Immediately before a cell divides the nucleus is resolved into chromatin fibres or threads and an achromatin matrix. These chromatin fibres are then marshalled into either rods or loops, &c., as the division of the cell proceeds (see Darwin and after Darwin, figs. 36, 37, and 38). Subsequent changes in the threads conclude the division (for a description of which consult the account above).

=Chromosomes.=—See Chromatin threads.

=Compositae.=—Plants in which the inflorescence consists of numerous small flowers brought together into a dense head, the base of which is enclosed by a common envelope (e.g. the Daisy, Dandelion, &c.).

=Congenital characters.=—See Plasmogenetic characters.

=Conjugation.=—This term is applied to a process observed in the Protozoa (q. v.), which seems to correspond to the sexual reproduction of the Metazoa (q. v.). The majority of the Protozoa cannot long continue to reproduce themselves a-sexually without becoming degenerate, or rather without becoming altogether extinct. Two individuals (as a rule) consequently unite either temporarily or permanently. In the former case, an exchange of material is effected; and in the latter, complete fusion takes place.

=Correlation.=—The normal coincidence of one phenomenon, character, &c., with another.

=Cytoplasm.=—See pp. 30 and 32.

=Determinant.=—See p. 123.

=Ectoblast.=—Syn. of epiblast and ectoderm. The general result of the division of a fertilized ovum is a two-layered ball of cells (a gastrula). The outer layer is called the ectoblast and the inner layer the entoblast. (See Darwin and after Darwin, p. 137 et seq.).

=Embryology.=—Hence embryogenesis, &c. The study of the development or the early growth of the individual.

=Entoblast.=—Syn. of hypoblast and endoderm. See Ectoblast.

=Epigenesis= (=Harvey=).—The theory that organisms are formed by the development of the egg itself, and not by the expansion of a miniature within the egg (preformation).

=Fallopian Tubes.=—The tubes through which the spermatozoa pass to effect fertilization, and through which the ova pass from the ovary to the uterus.

=Fission.=—Syn. of fissiparous separation. The breaking into two (without karyokinesis—q. v.) of a cell, which has, by overgrowth, disturbed its physiological equilibrium. This process is almost mechanical.

=Formative material.=—See p. 56.

=Gemmation.=—That form of a-sexual reproduction known as budding.

=Gemmules= (=Darwin=).—Minute granules, formed by the division of the general body-cells, which are supposed to be dispersed throughout the entire system. These themselves multiply by division, and are collected from all parts of the body to constitute the sexual elements.

=Germ-plasm.=—See p. 32.

=Hydroids.=—Belong to a division (Hydrozoa) of the stinging-animals or Coelenterata. They occur both in the sea and in fresh water, and are solely polypoid (i.e. tubular and tentacled).

=Hydromedusae.=—Also Hydrozoans. Hydroid colonies with special sexually reproductive persons, which are often liberated as floating bells or discs.

=Idio-plasm= (=A and B=).—See pp. 31 and 32.

=Ids.=—See p. 123.

=Invertebrata.=—Animals with a dorsal heart and without a backbone.

=Karyokinesis.=—The changes which are observed in the nucleus both immediately before and after cell division. See Chromatin threads.

=Lamarckian factors.= See Somatogenetic characters. Also Neo-Lamarckians.

=Metaphyta.=—Multicellular plants (q. v.).

=Metazoa.=—Multicellular animals (q. v.).

=Micellae= (=Nägeli=).—See Molecules, with which they are identical.

=Microaomata.=—The protoplasm of certain vegetable cells is in places characterized by the presence of minute corpuscles, which may be regarded as part of the protoplasm, and are certainly of a protoplasmic nature. These are termed Microsomata.

=Molecules= (=Weismann=).—See p. 122.

=Multicellular organisms.=—Organisms composed of many cells, as distinguished from the Unicellular organisms, where each individual is constituted of only one cell.

=Natural Selection.=—Survival of the Fittest in the struggle for existence. For a full account of the process see Darwin and after Darwin, p. 251 et seq.

=Neo-Darwinians.=—Those who believe that Natural Selection has been the only modifying influence in the evolution of species, and that the material for its action has been only plasmogenetic characters (q. v.).

=Neo-Lamarckians.=—Those who hold that organic evolution has been effected solely by means of the occurrence and preservation (inheritance) of somatogenetic characters (q. v.).

=Nuclear Thread or Loops.=—See Chromatin threads.

=Nucleo-plasm.=—See pp. 30 and 32.

=Nucleus.=—See Cell nucleus.

=Nutritive congenital characters.=—See p. 64.

=Ontogenetic grades.=—See p. 35.

=Ontogeny.=—The life history of the individual, as distinguished from the ancestral history of the race (Phylogeny).

=Ova.=—Eggs—the product of the female reproductive gland (ovary or ovarium).

=Ovule.=—The seed in its earliest condition.

=Pangenesis= (=Darwin=).—The theory of Heredity by gemmules (q. v.).

=Panmixia= (=Weismann=).—The condition of free intercrossing, i.e. where Natural Selection (q. v.) cannot act.

=Parthenogenesis.=—A degenerate form of sexual reproduction, in which the egg develops without having been fertilized by the male element.

=Phylogeny.=—The ancestral history of the race, as distinguished from the life history of the individual (Ontogeny).

=Physiological Units= (=Spencer=).—Special units which it is inferred a plant or animal of any species is made up of, and in all of which dwells the intrinsic aptitude to aggregate into the form of that species.

=Plasma.=—The constituent material of cells, e. g. germ-plasma (of sexual-cells), somatoplasma (of body-cells).

=Plasmogenetic characters.=—Variations due to admixtures of germ-plasm in acts of sexual fertilization (and therefore present at birth), as distinguished from somatogenetic characters—variations which have been acquired independently of germ-plasm. See Somatogenetic characters.

=Polar bodies.=—Before an egg is fertilized the nucleus moves towards the periphery and divides twice. The two cells that are thus formed are the polar bodies. The extrusion of polar bodies is probably universal among animals, but only one polar body is extruded from parthenogenetic ova. See Darwin and after Darwin, pp. 125 and 126.

=Preformation.=—The old conjecture (1672—Malpighi) that the development of an embryo was merely the expansion or unfolding of a miniature of the adult within the egg.

=Protophyta.=—Unicellular plants (q. v.).

=Protoplasm.=—Living matter.

=Protozoa.=—Unicellular animals (q. v.).

=Representative Congenital characters.=—See p. 65.

=Reversion.=—See Atavism.

=Rudimentary Organs.=—Usually considered a synonym of the term “vestigial characters,” and is the name under which are included all those organs which, either from having become useless or from other causes, have been much reduced in size, e.g. the muscles of the external ear in man (see Darwin and after Darwin, p. 76), &c. Latterly the former expression has been used to describe organs in process of development (e.g. the electric organ of the skate—loc.cit., p. 365 et seq.), whilst the latter is made to embrace all those organs in process of elimination.

=Soma.=—A general term descriptive of the whole mass of the body-cells of an organism.

=Somatic-idio-plasm.=—See p. 32.

=Somatogenetic characters.=—Characters acquired by the soma (i. e. variations acquired after birth by the action of the environment), as distinguished from characters produced and potentially present from the first by a union of two masses of germ-plasm—plasmogenetic characters (q. v.).

=Somatoplasma-plasm.=—See p. 32.

=Specialized congenital characters.=—See p. 65.

=Spermathecae.=—Organs for the storing of the seminal fluid received in copulation.

=Spermatogenesis.=—The precise development of spermatozoa.

=Spermatozoa.=—The essential elements in the male seminal fluid, and secreted by the testis—the male reproductive gland.

=Stirp= (=Gallon=).—See p. 58.

=Telegony.=—See p. 141.

=Unicellular Organisms.=—Organisms composed of a single cell only, as distinguished from those consisting of aggregations of cells—Multicellular organisms.

=Vertebrata.=—Animals with a backbone and a ventral heart.

=Vestigial Organs.=—See Rudimentary organs,

=Xenia.=—See p. 141.

INDEX.

Acquired characters, definition of, 5; inheritance of, 6, 15, 49, 57, 60, 67, 69, 71, 81, 83-84, 93-96, 104, 107, 110-111, 127, 173, et seq.; Galton on inheritance of, 62, 106.

Adaptive development, Weismann on, 19.

Algae, De Vries on the chromatophores of, 83, 111.

Amphigony, the cause of individual hereditary variation, 91, 100-101.

Amphimixis, see Sexual propagation.

Ancestral germ-plasm, 123.

Atavism, 3, 91, 105.

=Bary, De=, on Weismann’s theory, 152.

Basidiomycetes, 90.

Begonia, regeneration in, 4, 52.

Biophores, 123.

Body-cells, and germ-cells, 29.

=Brooks=, theory of heredity, 2.

Bud-variation, 90, 94, 96, 98-99; Weismann on, 95, 97, 161; Fritz Müller on, 95.

Butterflies, climatic varieties of and Weismann’s theory, 67-68, 127-128.

=Candolle, De=, on inheritance of acquired characters in plants, 93. “Carriers of Heredity,” 32, 38, 70, 78, 122.

Cessation of Selection, see Panmixia.

Chromatophores, of Algae, 83, 111.

Compositae, pollen of, 5.

Congenital variations, definition of, 5; inheritance of, 6, 110; sexual propagation, the cause of, 11; Darwin on, 13; origin of, 23, 25, 100, 102; nutritive congenital changes, 64; examples of, 64; specialized congenital changes, 65; representative congenital changes, 65; Galton on, 134.

Continuity of germ-plasm, see Germ-plasm.

Crustacea, and the inheritance of acquired characters, 94.

Cuttings, and bud-variation, 98.

Cytisus adami, grafting of, 127.

=Darwin, Charles=, and Pangenesis, 2, 26; arguments in favour of pangenesis, 3, 59; on the cause of congenital variations, 13; comparison of his theory of heredity with that of Weismann, 52, 55, 73, 92, 105-106, 115, 133, 173 et seq.; on germ and somatic-cells, 76; on the influence of pollen upon somatic tissues, 79-80; on graft-hybridization, 83; on bud-variation, 95; on the causes of variation, 102, 161; on the inheritance of acquired characters, 107, 111-112; on Xenia, 144; on sexual union, 154.

Death, Weismann on the origin of, 8, 10; in plants, 10.

Determinants, 123.

Direct action of environment, on unicellular organisms, 15, 23.

=Elsberg=, theory of heredity, 2.

Environment, direct action of on Protozoa, 15.

Evolution, see Organic evolution.

=Flint, Prof. Austin=, on Telegony, 204.

=Focke=, on Xenia, 141, 144.

“Formative material,” and germ-plasm, 56.

Fungi, Prof. Vines on Basidiomycetes, 90.

=Galton, Francis=, theory of heredity (stirp), 2; and Weismann’s, 51, 58-59, 69, 73, 92, 105-106, 108, 115, 129, 130 et seq.; on gemmules, 60; on inheritance of acquired characters, 62, 69, 107; and stability of the material basis of heredity, 63; on origin of sexual reproduction, 103, 167.

=Gärtner=, on Malva, 80; on inheritance of acquired characters in plants, 93.

Gemmules, 2; Darwin on the size of, 4; and germ-plasm, 52, 55, 58, 92, 105; and stirp, 58; Galton on, 60.

Generative cells of the Hydromedusae, Weismann on, 71, 109; example of continuity of germ-plasm, 72-73.

Germ-cells, and body-cells, 29, 75-77; nucleo-plasm of, 30; number of, 43, 45.

Germ-plasm, Weismann’s theory of, 5, 105, 173 et seq.; immortality of, 9, 24; continuity of, 9, 18, 49, 56-67, 69-70, 72, 75, 78, 86-87, 104-105, 109-110, 114, 120, 168; differences in, 12; origin of, 17; independence of, 19; and natural selection, 21; stability of, 22, 49, 57, 66, 86-89, 91-93, 99-100, 104-105, 109, 112-114, 151 et seq.; lodged in nucleus, 29; and somato-plasm, 29, 81, 110; the modification of, 36; examination of Weismann’s theory of, 48; Weismann’s theory of and Pangenesis, 52; and gemmules, 52, 55, 58, 105-106, 121; multiplication of in the general cellular tissues of plants, 53; De Vries on, 54; Differentiation of, 55; and “formative material,” 56; and stirp, 58-59, 61, 75, 106; and somatic-idioplasm, 69; as a basis of heredity, 70; ancestral germ-plasm, 123.

Grafting, and the effect of the somatic-tissues on the germinal elements, 81-82; Darwin on, 83; and bud-variation, 98; Weismann on, 126.

=Häckel=, theory of heredity, 2.

=Hartog, Prof. M.=, on Weismann, 155; on sexual propagation, 166-167.

Healing of wounds, 34.

=Henslow, Rev. G.=, on regeneration in plants, 53.

Heredity, various theories of, 2, 49, 70; statement of Weismann’s theory of, 17; modification of Weismann’s theory of, 28, 46, 52, 65, 68, 75, 163 et seq.; the nucleus and, 29; “carriers of,” 32, 38, 70, 78, 122; theory of and histology, 38; examination of Weismann’s theory of, 48, 105, 117; comparison of Weismann’s, Darwin’s, and Galton’s theories of, 51, 105-106; criticism of Weismann’s theory of by Strasburger, 51; the material basis of, 61, 63.

=Hertwig, O.=, theory of heredity, 2; on polar bodies, 46, 125.

=Hildebrand=, or effect of pollen upon somatic tissues (Xenia), 80; on Orchideae, 80.

=His=, theory of heredity, 2.

=Hoffmann=, on the inheritance of acquired characters, 93-4, 114.

Hydromedusae, Weismann on generative cells of, 71, 109; illustrate continuity of germ-plasm, 73-73.

Identical twins, 41.

Idio-plasm, Nägeli’s term, 31; A and B, 31-32; self-multiplication of, 34; amount of idio-plasm A in the nucleus, 40.

Ids, 123.

Individual differences, Weismann, 39, 41, 43.

Influence of a previous sire upon the progeny of the same dam, see Telegony.

Influence of external conditions, see Acquired characters.

Influence of pollen upon somatic tissues, see Xenia.

Inheritance of acquired characters, see Acquired characters.

Invertebrates, Weismann on sexual apparatus of, 72, 74, 109.

Jelly-fish, regeneration in, 4.

=Jordan=, on inheritance of acquired characters in plants, 93.

Karyokinesis, 37.

=Lamarck=, Weismann and, 16, 21.

Lamarckian factors, importance of, 57, 59, 62, 65, 67, 69, 82, 106-108, 111-112, 128, 147.

Life, duration of, 7, 10.

=Malingié-Nouel=, on Telegony, 193 et seq.

Malva, Gärtner on, 80.

=Maupas=, on the Protozoa, 101, 148.

Metazoa and Metaphyta, cause of mortality of, 7, 24, 148; relation of progeny to parents in, 16; transmission of acquired characters in, 16; propagation in, 51.

=Mivart=, on inheritance of acquired characters, 94.

Molecules, 54, 123.

=Morton, Earl of=, on Telegony, 192.

=Müller, Fritz=, on bud-variation, 95.

Multicellular organisms, see Metazoa and Metaphyta.

=Nägeli=, theory of heredity, 2; and idio-plasm, 31, 187; and germ-plasm, 36; on inheritance of acquired characters in plants, 93.

Natural selection, the cause of death, 8; action of, 20; the material for the operation of, 13, 57; not the cause of sexual propagation, 13-14; and the Protozoa, 15, 101-102; and germ-plasm, 21; sole cause of organic evolution, 25, 59, 111, 114.

=Nouel, Malingié=, on Telegony, 193 et seq.

Nucleo-plasm, of germ and somatic cells, 30.

Nucleus, alone contains germ-plasm, 29; contains two substances, 33; and heredity, 37; and polar bodies, 40; amount of idio-plasm A in, 40.

Nutritive congenital changes, 64.

Orchideae, Hildeband on, 80.

Organic evolution, the cause of, 25; Weismann’s theory of, 26, 48, 50, 58, 66, 68, 87, 100, 104, 106-108, 114-115, 147.

Ova, Weismann on the size of, 39.

=Pallas=, on variability, 154.

Pangenesis, Darwin’s theory of, 2, 26; and Weismann’s theory of, 52, 55, 71, 73, 121; and Panmixia, 59-60; Galton on, 60.

Panmixia, and Pangenesis, 59-60.

Parthenogenetic organisms, and natural selection, 15; no congenital variations in, 72, 75.

Parthenogenetic ova, Weismann on, 45, 89, 91, 109.

Phylogenesis, 34.

Physiological isolation, of germ-cells, 74.

Plants, reproductive cells of, 74; influence of pollen upon somatic tissues of (Xenia), 78-80; bud-variation in, 90, 94-99; Hoffmann’s investigations on the inheritance of acquired characters in, 93.

Polar bodies, Weismann on, 40, 46, 125; examination of Weismann’s explanation of, 42; O. Hertwig on, 46, 125.

Protophyta, natural selection and, 114.

Protozoa, immortality of, 7; and natural selection, 15, 114; origin of species of, 15, 102; action of environment on, 15; Maupas on, 101.

Regeneration, in sea-anemones and jelly-fish, 4, 35; of an entire organism, 34; Weismann on, 51 et seq.; in Begonia, 52; Rev. G. Henslow on, 53; and stirp, 59.

Rejuvenescence, 166.

Representative congenital changes, 65.

Reproduction, essential meaning of sexual, 8, 11; in the Protozoa, 16; somatic, 35.

Reproductive elements, potential immortality of, 9; of Vertebrates and Plants, 74.

Reversion, 3, 91, 105.

=Roux=, on the principle of “struggle,” 139.

Sea-anemones, regeneration in, 4.

Sexual apparatus of Invertebrates, Weismann on, 72, 74.

Sexual-cells and somatic-cells, 75-77, 81, 84.

Sexual propagation, essential meaning of, 8, 11, 87; sole cause of congenital variations, 12, 89-90, 102, 135, 141, 153, 158; did not arise through the agency of natural selection, 13-14; in multicellular organisms, 51; Galton on the origin of, 103; in Cytisus adami, 127.

Significance of sexual reproduction, see Sexual Reproduction.

Somatic-cells, nucleo-plasm of, 30; and sexual cells, 75-77, 81, 84.

Somatic-idio-plasm, 32-33; and germ-plasm, 69.

Somatic reproduction, 35, 52.

Somato-plasm and germ-plasm, 29.

Specialized congenital changes, 65.

Species, Weismann on the origin of new, 100-101.

=Spencer, Herbert=, theory of heredity, 2; on Telegony, 191 et seq.

Stability of germ-plasm, see Germ-plasm.

Stirp, and gemmules, 58-59, 61; and somatic tissues, 60; and the germinal cells of Hydromedusae, 73; and germ-plasm, 75, 92, 106, 133.

=Strasburger=, on Weismann’s theory of heredity, 51; on the origin of sexual propagation, 167.

Stylonichia, Maupas on, 101.

Summary, 103.

Telegony, 77-79, 110, 141 et seq., 191 et seq.

Transmission of acquired characters, see Acquired characters.

Twins, identical, 41.

Unicellular organisms, reproduction of, 16; action of environment on, 23, 147 et seq.; potentially immortal, 23; natural selection and the, 24, 57, 114; and the origin of hereditary individual variations, 100.

Variation, see Congenital variations, Acquired characters, &c.; Darwin on the causes of, 102; Weismann on the origin of, 153.

Vertebrates, reproductive cells of, 74.

Vestigial organs, persistence of, 91.

=Vines, Prof. S.=, criticism on Weismann, 14, 75, 90, 99, 152, 178; on the Basidiomycetes, 90.

=Vries, De=, theory of heredity, 2; on germ-plasm, 54; on the chromatophores of Algae, 83, 111; on Xenia, 144.

=Weismann, Prof. August.=, theory of germ-plasm, 5, 17, 173 et seq.; on the duration of life, 7, 10; on the essential meaning of sexual propagation, 11, 103, 135, 141; on natural selection as the origin of sexual reproduction, 14; on Prof. Vines’ criticism, 14, 90, 99, 178 et seq.; on the Protozoa and natural selection, 15, 102; on Lamarck, 16; on adaptive development, 19; and natural selection, 21; summary of theory of germ-plasm, 23; theory of organic evolution, 26, 48, 50, 58, 66, 68, 87, 100, 104, 106-108, 114-115, 147; modifications of theory of heredity, 28, 46, 52, 65, 68, 75, 163 et seq.; and of self-multiplication of idio-plasm, 34; on “ontogenetic grades,” 35, 53; on the modification of germ-plasm, 36; on chromatin, 38; on individual differences, 39, 41, 43; on the size of ova, 39; on polar bodies, 40, 42, 46, 125; on the number of germ-cells, 44-45; on parthenogenetic ova, 45, 89, 91; examination of his theory of germ-plasm or heredity, 48, 85; on the stability and continuity of germ-plasm, 49, 63, 66, 86-89, 91-93, 99-100, 103-105, 107, 109-110, 112-114, 120, 151, 158; comparison of his theory with those of Darwin and Galton, 51, 58; on Strasburger’s criticism of his theory, 52; on the multiplication of germ-plasm in the general cellular tissues of plants, 53; on regeneration in plants, 53; anticipated by Galton, 59, 68; and Galton, 63, 130 et seq.; on transmission of acquired characters, 67, 83, 96, 111, 127; and his critics, 70; on the Hydromedusae, 71, 109; on the sexual apparatus of Invertebrates, 72; and the influence of germ-cells upon somatic tissues (Telegony and Xenia), 80-81, 196 et seq.; and the significance of grafting, 81-82, 126; and vestigial characters, 92; on Hoffmann’s investigations, 93; on bud-variation, 95, 97, 161; on the origin of hereditary individual variations, 100-101; on the origin of new species, 101.

Wounds, healing of, 34.

Xenia, 78-81, 110, 141, 144, et seq.

THE END.

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FOOTNOTES:

Considerable portions of this chapter have already appeared as an article in the Contemporary Review for May, 1890. My thanks are due to the editor for kindly allowing me to reproduce them here.

In as far as these sundry theories of heredity are not more or less intermediate between those of Darwin and Weismann, the differences have reference either to points of comparative detail, or else to the introduction of ideas derived from chemistry and physics—whereby it is sought to show that the principles of chemical combination and of rhythmic vibration may have a more or less considerable share in the matter. For my own part I do not see that the introduction of such ideas has been of any avail in helping—even hypothetically—to explain the phenomena of heredity; and therefore I do not deem it worth our while to consider them.

See Appendix.

E.g., Variation, &c., vol. i. pp. 197, 398; vol. ii. pp. 237, 252.

Since this chapter was written and sent as a contribution to the Contemporary Review, Professor Weismann has published in Nature (Feb. 6. 1890) an elaborate answer to a criticism of his theory by Professor Vines (Oct. 24, 1889). In the course of this answer Professor Weismann says that he does attribute the origin of sexual reproduction to natural selection. This directly contradicts what he says in his Essays; and, for the reasons given in the text, appears to me an illogical departure from his previously logical attitude. I herewith append quotations, in order to reveal the contradiction.

“But when I maintain that the meaning of sexual reproduction is to render possible the transformation of the higher organisms by means of natural selection, such a statement is not equivalent to the assertion that sexual reproduction originally came into existence in order to achieve this end. The effects which are now produced by sexual reproduction did not constitute the causes which led to its first appearance. Sexual reproduction came into existence before it could lead to hereditary individual variability [i.e., to the possibility of natural selection]. Its first appearance must, therefore, have had some other cause [than natural selection]; but the nature of this cause can hardly be determined with any degree of certainty or precision from the facts with which we are at present acquainted.”—Essay on the Significance of Sexual Reproduction in the Theory of Natural Selection. English Translation, pp. 281-282.

“I am still of opinion that the origin of sexual reproduction depends on the advantage which it affords to the operation of natural selection.... Sexual reproduction has arisen by and for natural selection as the sole means by which individual variations can be united and combined in every possible proportion.”—Nature, vol. xli. p. 322.

How such contradictory statements can be reconciled I do not perceive; but they furnish a good example of the extreme laxity with which the term “natural selection” is used by ultra-Darwinians.

The meaning of this term, however, as originally used by Nägeli, he so greatly changes to suit the requirements of his own theory, that I think it would have been better had he coined some new one.

I think it is to be regretted that for this other kind of idio-plasm (i.e., idio-plasm-B) Weismann has not coined some distinctive name, or some distinctive prefix, such as that which he sometimes employs when speaking of the other kind (i.e., idio-plasm-A)—viz., “somatic-idioplasm.” Also, the interchangeable manner in which he uses his term “idio-plasm” with the term “ nucleo-plasm,” is somewhat confusing (e.g., pp. 217, 219, 220, 250, 251, &c.). I may add that the word “plasm” in all its combinations appears to me an unfortunate one, since it seems to betoken a substance that can be seen, instead of merely inferred. But, be this as it may, the following table of terms employed may be useful for ready reference:—

Nucleo-plasm = the whole contents of the nucleus of any cell.

Cytoplasm = all the other contents of any cell.

Idio-plasm-A = that portion of nucleo-plasm which “controls” a single cell.

Idio-plasm-B = that portion of nucleo-plasm which is destined to construct future cells.

Germ-plasm = undifferentiated idio-plasm-B.

Somato-plasm = idio-plasm-A + cytoplasm.

See close of Appendix.

See Part I, figs. 36, 37, and 38. The substance of this thread, in the various phases of its segmentation, is the “chromatin,” as there depicted, and so called because it takes a stain better than other parts of the nucleus—thus showing some distinctive character.

For an account of the formation and expulsion of these bodies, see Part I, pp. 125-6. There is now no longer any doubt touching the statement there made as to the male-cell likewise parting with some of its nuclear substance prior to fertilizing the female.

In the case of identical twins, both are probably always produced from the same ovum.

We have no means of estimating exactly the proportional number of cases in which this is possible, either among the lower or the higher plants; but it is certainly much greater than Weismann supposes. “How is it that all plants cannot be reproduced in this way?” he asks, and then adds,—“No one has ever grown a tree from the leaf of a lime or an oak, or a flowering plant from a leaf of the tulip or the convolvulus.” But I am told by botanists that the only reason why the phenomenon thus appears to be a rare one, is because it is not worth anybody’s while to grow plants in this way at a necessarily unsuitable season of the year. Thus, the Rev. George Henslow writes me:—“The fact is that any plant will reproduce itself by its leaves, provided that the cells be ‘embryonic,’ (i.e., the leaf not too near its complete development), and that it be not too thin, so as to provide enough nutriment for the bud to form till it has roots.”

Intracellulare Pangenesis, s. 55.

I employ the term “particles,” instead of “molecules,” because although Weismann and his followers seem to prefer the latter term, I can scarcely imagine that they intend to use it in its original, or chemical, sense.

This principle will be considered at some length in my next volume.

Galton first published his theory in 1872 (Proc. R. S., No. 136), but presented it in a more complete form three years later (Contemporary Review, Dec. 1875, and Journl. Anthropol. Inst., 1875).

Journ. Anthropol. Inst. 1875, p. 346.

Essays, &c., 2nd ed., p. 105.

Essays, &c., 2nd ed., p. 100.

See for example, Essays, p. 229.

On previous occasions, when inconsistencies have been brought to the notice of Professor Weismann by his critics, he has complained that sufficient allowance was not made for the fact of his having published his sundry essays at different times. This, of course, is a satisfactory answer in cases where criticism refers to a growing theory, the later additions to which supersede certain parts of the earlier construction. But clearly the answer is not available in cases where one set of statements, touching fundamental principles of the theory, are directly opposed to others. A logical contradiction is not affected by dates of publication, and where the contradictory statements have reference to the vital essence of a theory, it is equally impossible for the theory to comprise them whether they be presented simultaneously or successively.

The possibility of any spermatozoa of the first impregnation surviving to take part in the second is excluded by the fact that the phenomenon occurs in mammals, and, apparently, may extend over two or three litters.

Possibly the school of Weismann may simply refuse to accept the facts, which are confessedly rare, and, in many of the cases alleged, dubious. In other cases, however, the evidence is sufficient to have satisfied the cautious judgement of Darwin, who has discussed it in detail. Therefore, even if the Neo-Darwinians repudiate this evidence, at least they ought to state that such is the position which they adopt.

Nature, Feb. 6th, 1890.

Nature, vol. xl. p. 626.

Ibid., vol. xli. p. 322.

In his Essays (vol. i. p. 282) Weismann says:—“If it could be shown that a purely parthenogenetic species had become transformed into a new one, such an observation would prove the existence of some new force of transformation other than selective processes, for the new species could not have been produced by these latter.” But now it has been shown that a purely parthenogenetic species can be transformed into a new one, and therefore it seems desirable to note that the observation does not so much as tend to prove the existence of some new force of transformation other than selective processes. For this most singular statement can only stand on a prior acceptance of Weismann’s own assumption, as to amphigony being the only possible cause of individual hereditary variation. Only if we have already, and with absolute certainty, embraced the whole Weismannian creed, could we consent to affirm that “natural selection is an impossibility in a species propagated by a-sexual reproduction.”

What he says is:—“It was only after a greater or less number of generations had elapsed that a variable proportion of double flowers appeared, sometimes accompanied by changes in the leaves and in the colours of the flowers. This fact admits of only one interpretation:—the changed conditions at first produced slight and ineffectual changes in the idio-plasm of the individual, which was transmitted to the following generation.... Now, the idio-plasm of the first ontogenetic grade (viz., germ-plasm) alone passes from one generation to another, and hence it is clear that the germ-plasm itself must have been gradually changed by the conditions of life, until the alteration became sufficient to produce changes in the soma, which appeared as visible characters in either flower or leaf.”—Essays, pp. 426-7; italics mine.

Nature, Nov. 14, 1889, p. 41.

Essays, 2nd Ed., pp. 331-2.

Essays, p. 296.

In this connexion it ought to be observed that Darwin believed the causes of variation to be internal as well as external—or arising from “the nature of the organism” no less—or even more—than from “changed conditions of life.” But although he appears to have entertained the admixture of hereditary endowments in sexual unions as one of the causes of variation belonging to the former category, he expressly says that he did not regard it as the only, or even the main, cause. (See Variation, &c., vol. i, pp. 197, 398; vol. ii, pp. 237, 252.)

See above, p. 54, note.

See Darwin and after Darwin, Part I, p. 129.

It must always be remembered that the view adopted by Weismann touching the nucleus (and more especially the chromosomes) of a germ-cell being the sole seat of heredity, is still far from having been established.

Essays, vol. ii. p. 122.

The Germ-plasm, p. 342.

The Germ-plasm, p. 342.

See, however, p. 83, note.

Essays, vol. i. p. 101. Italics mine.

The Germ-plasm, p. 406.

Galton, loc. cit., pp. 343-344.

Professor Weismann still maintains that there is a further important distinction between the theories of pangenesis and germ-plasm, in that the one is pre-formative while the other is epigenetic. But I am still unable to perceive that such is the case. He argues, indeed, that his new doctrine of determinants emphasizes this distinction: the argument, however, appears to me radically unsound. For instance, he says, “The hereditary continuation in each part is pre-determined in each part from the germ onwards. The right and left ears could not possibly resemble each other, if the relative strength of the hereditary tendencies on both sides were not pre-determined for all parts of the child by the nature of the paternal and maternal idants.” Very well. But, if so, the theory of determinants is just as much pre-formative as is that of gemmules. Or, conversely, the latter is quite as epigenetic as the former. Both are alike determinative, while neither supposes that the determination is due to a pre-formed miniature of the future child in the fertilized egg of its mother; but to a particulate representation in the latter of every heritable part of the former.

By “germ” Galton means a carrier of heredity, which is capable of self-multiplication. In these fundamental respects, therefore, it is equivalent to a “gemmule” on the one hand and a “determinant” on the other. The three terms are so far synonymous.

Loc. cit., p. 338.

Loc. cit., p. 339.

The Germ-plasm, pp. 199, 220.

pp. 72-4.

The Germ-plasm, pp. 383-386.

Quoted from above, p. 78.

Morph. Journal, vol. ii.

See Appendix II.

Essays on Heredity, vol. ii. pp. 193-4.

See above, pp. 63-67.

Nature, vol. xli. p. 322.

The Germ-plasm, pp. 414-415. Italics Weismann’s.

Essays, vol. i. p. 284.

The Germ-plasm, p. 431.

Variation &c., vol. i. p. 398.

Ibid., vol. ii. p. 242.

Nature, May 11, pp. 28-29.—In 1891-2 Professor Hartog furnished a criticism of Weismann’s theory of Heredity (Nature, vol. 44. p. 613, and Contemporary Review, July, 1892). Although disputed at the time by some of Weismann’s followers in England, this criticism was one of unquestionable cogency, and has now been recognized as such by Weismann himself (The Germ-plasm, pp. 434-5). The main point of the criticism had been missed by previous critics of Weismann, and consisted in revealing an important “difficulty” inherent in the structure of the theory itself. How far this criticism had the effect of causing Professor Weismann to abandon his theory of variation being exclusively due to amphimixis, as Professor Hartog appears to think (Nature, May 11, 1893, p. 28), is immaterial. But it must be observed that as far back as February, 1890, Professor Weismann in his answer to Professor Vines’ criticism wrote the passage already quoted on page 152.

It is almost needless to say that no fault is to be found with Weismann for having thus reversed his opinion touching one of his fundamental postulates. Consistency is no merit in a man of science; and least of all where matters of such high speculation are concerned. I think, however, that it is open to question whether an author of any kind should suffer an elaborate system of theories to be published and translated, at the very time when he is himself engaged in producing another work showing the untenable character of their basal premises. At any rate, it would have saved his English readers no small trouble and confusion, if Weismann had added notes to the translations of his essays on Polar Bodies, on The Significance of Sexual Reproduction, and on Amphimixis, to the effect that he had abandoned some of their most distinctive features before the translations had gone to press.

See especially pp. 86-89. All that is there said about the unicellular organisms is not, in the present connexion, affected by Weismann’s change of view with regard to them. We have only to substitute “primordial” or “protoplasmic” for “unicellular,” and nearly all the points of the criticism remain.

Professor Weismann has now considered more fully than heretofore the phenomena of bud-variation (The Germ-plasm, pp. 439-442); but as he continues (though with diffidence) to take substantially the same view of them as that which I have already quoted on pp. 95-96, it is needless for me to re-discuss the matter here.

“Rejuvenescence” means the renewal of vital energies which is supposed to result from a fusion of the contents of two cells. For an excellent discussion of this and the other theories on the object of sexual propagation, see a brief article by Professor Marcus Hartog, in the Contemporary Review for July, 1892. Since then Weismann has published The Germ-plasm, and here his main argument against this theory is that tens, or even hundreds of generations of unicellular organisms have been observed to succeed one another before any act of conjugation takes place. But I cannot see that it signifies how many generations may in different species be proved capable of resulting from a single act of conjugation. Weismann himself now accepts the analogy between cell-proliferation as resulting from conjugation in unicellular organisms, and from fertilization in multicellular. But even three hundred generations of the former can scarcely be regarded as equal to all the “ontogenetic stages” of the latter.

This view of the function of sexual propagation is now universally ascribed to Strasburger, and it is quite true that he has independently adduced it. But as this was not done until about ten years after it had been published by Galton, I have designedly associated the idea with Galton’s name. The following are the words in which it was announced by him:—

“The necessity of a system of double parentage in complex organisations is the immediate consequence of a theory of organic units and germs, as we shall see if we fix our attention upon any one definite series of unisexual descents, and follow out its history. Suppose we select, cut off, and plant the second bud, then after it has grown to maturity we similarly take the second of its buds, and so on consecutively. At each successive stage there is always a chance of some one or more of the various species of germs in the stirp dying out, or being omitted; and of course when they are gone they are lost for ever, and are irreplaceable by others. From time to time this chance must fall unfavourably, and will cause a deficiency in some of the structural elements, and a consequent deterioration of the race. If the loss be vital, this particular line of descent will of course be extinguished at once; but on the more favourable supposition, the race will linger on, submitting to successive decrements in its constituent elements, until the accumulation of small losses becomes fatal.”—loc. cit., p. 333.

Galton also points out a further advantage that is secured by “amphimixis,” and one which shows the non-necessity of what remains of Weismann’s theory of polar bodies, thus:—

“There is yet another advantage in double parentage, namely, that as the stirp whence the child sprang can only be half the size of the combined stirps of his two parents, it follows that one half of his possible heritage must have been suppressed. This implies a sharp struggle for place among the competing germs, and the success, as we may infer, of the fitter half of their numerous varieties.”—loc. cit., p. 334.

In fact, it seems to me that this is the sole supposition whereby it can be held that sexual propagation has been developed both “by” and “for” natural selection, in order to supply variations as material for the action of this principle. Natural selection cannot thus supply the conditions to its own activity, if, as Weismann supposes, there is but one purpose for it to subserve (see above, pp. 13-15). But, if it is acting for more than one purpose, the “by” and the “for” argument may hold.

I find that a passage explaining the sense in which I use these terms has been accidentally omitted from Chapter III, where they are first introduced; and, as the sheets of that chapter have been already printed off, I here supply the omission. The terms in italics are not Weismann’s, and I have employed them merely for the purpose of giving precision to his views. By “absolute stability of germ-plasm” I mean to indicate that degree of stability which he has hitherto postulated as the necessary basis for his doctrine of heritable variations being solely due to admixtures of germ-plasm in sexual unions. By “perpetual continuity of germ-plasm” I intend to denote that amount of continuity which he still postulates as the necessary basis for his correlative doctrine touching the non-inheritance of acquired characters.

Essays, pp. 76-77, from which the following quotations are likewise taken seriatim.

“Or, more precisely, they must give up as many molecules as would correspond to the number of the kind of cell in question found in the mature organism.” Of course by “molecules” Weismann means what Darwin does by “gemmules.”

If there are such things as gemmules, it appears to me to follow that the only physiological distinction between the reproductive glands and glands in general is, that the former discharge their products in the form of living cells. Even here, however, there appears to be one analogous case in those salivary glands which discharge the so-called salivary corpuscles—i.e., nucleated cells, undergoing amoeboid changes of form, and exhibiting the movements of living protoplasm in their interior.

Variation, &c., 2nd ed., vol. ii. pp. 374-6.

Nature, vol. xl. p. 624. Weismann’s answer to this and other parts of Professor Vines’ criticism where the term “somato-plasm” occurs, will be considered later on.

Weismann speaks disparagingly of Darwin’s theory as a “theory of preformation” (p. 316). “We must assume,” he adds by way of explanation, “that each single part of the body at each developmental stage is, from the first, represented in the germ-cell as distinct particles of matter, which will reproduce each part of the body at its appropriate stage as their turn for development arrives.” But must we not likewise “assume” exactly the same thing in the case of Weismann’s own theory? To me, at any rate, it appears that the description is quite as appropriate to germ-plasm as it is to gemmules. Nor can I see any distinction, even where he seeks to draw it more expressly, as for instance—“Every detail in the whole organism must be represented in the germ-plasm by its own special and peculiar arrangement of the groups of molecules, ... not indeed as the pre-formed germs of structure (the gemmules of pangenesis), but as variations in its molecular constitution.” [Essays, p. 194.] Again, on page 325 he gives a foot-note explaining the distinction by alluding to the controversy between the preformationists and epigenesists. But the theory of pangenesis does not suppose the future organism to exist in the egg-cell as a miniature: it supposes merely that every part of the future organism is represented in the egg-cell by corresponding material particles. And this, as far as I can understand, is exactly what the theory of germ-plasm supposes; only it calls the particles “molecules,” and seemingly attaches more importance to the matter of variations in their arrangement or “constitution,” whatever these vague expressions may be intended to signify.

‘Philosophical Transactions of the Royal Society for the Year 1821,’ Part I. pp, 20-24.

Readers who may happen to be acquainted with De Vries’ important essay on heredity will perceive how well this suggestion fits in with his modification of Pangenesis.

As already indicated, I cannot gather from his remarks on the subject which, if any, of the alternative interpretations of the phenomena that we are considering Mr. Spencer adopts. From the following sentences it would appear that he assigns yet a third interpretation, and this as the only possible one. For he says of these phenomena: “They prove that while the reproductive cells multiply and arrange themselves during the evolution of the embryo, some of their germ-plasm passes into the mass of somatic cells constituting the parental body, and becomes a permanent component of it. Further, they necessitate the inference that this introduced germ-plasm, everywhere diffused, is some of it included in the reproductive cells subsequently formed” (Contemporary Review, March, p. 452). This appears to mean that the influence of a previous sire can only be explained by supposing that the developing embryo inoculates the somatic tissues of its mother with hereditary material derived from its father, and that the maternal tissue afterwards reflect some of this material (or its influence) to the still unripe ovarian ova. If this be the hypothesis intended, it seems to me more complex than any of the three which I have suggested. But, be this as it may, we certainly cannot agree that such an hypothesis is “proved” by the facts, or that the latter “necessitate” the inference as to its being some of the embryo’s germinal matter which enters the unripe ova.

“A Text Book of Human Physiology.” By Austin Flint, M.D., LL. D. Fourth edition. New York: D. Appleton & Co. 1888. Page 797.