“In such a case we have only to assume that the climate which is unfavourable, and nutriment which is insufficient for horses, affect not only the animal as a whole but also its germ-cells. This would result in the diminution in size of the germ-cells, the effects upon the offspring being still further intensified by the insufficient nourishment supplied during growth. But such results would not depend upon the transmission by the germ-cells of certain peculiarities due to the unfavourable climate, which only appear in the full-grown horse.”
But Professor Weismann does not like such cases, and admits that he cannot explain the facts in connection with the climatic varieties of certain butterflies, except “by supposing the passive acquisition of characters produced by the direct influence of climate.”
Nevertheless, in his next paragraph but one he calls such cases “doubtful,” and proposes that for the moment they should be left aside. He accordingly leaves them, but I have not yet found what other moment he considered auspicious for returning to them. He tells us that “new experiments will be necessary, and that he has himself already begun to undertake them.” Perhaps he will give us the results of these experiments in some future book—for that they will prove satisfactory to him can hardly, I think, be doubted. He writes:—
“Leaving on one side, for the moment, these doubtful and insufficiently investigated cases, we may still maintain that the assumption that changes induced by external conditions in the organism as a whole are communicated to the germ-cells after the manner indicated in Darwin’s hypothesis of pangenesis, is wholly unnecessary for the explanation of these phenomena. Still we cannot exclude the possibility of such a transmission occasionally occurring, for even if the greater part of the effects must be attributable to natural selection, there might be a smaller part in certain cases which depends on this exceptional factor.”
I repeatedly tried to understand Mr. Darwin’s theory of pangenesis, and so often failed that I long since gave the matter up in despair. I did so with the less unwillingness because I saw that no one else appeared to understand the theory, and that even Mr. Darwin’s warmest adherents regarded it with disfavour. If Mr. Darwin means that every cell of the body throws off minute particles that find their way to the germ-cells, and hence into the new embryo, this is indeed difficult of comprehension and belief. If he means that the rhythms or vibrations that go on ceaselessly in every cell of the body communicate themselves with greater or less accuracy or perturbation, as the case may be, to the cells that go to form offspring, and that since the characteristics of matter are determined by vibrations, in communicating vibrations they in effect communicate matter, according to the view put forward in the last chapter of my book Luck or Cunning, then we can better understand it. I have nothing, however, to do with Mr. Darwin’s theory of pangenesis beyond avoiding the pretence that I understand either the theory itself or what Professor Weismann says about it; all I am concerned with is Professor Weismann’s admission, made immediately afterwards, that the somatic cells may, and perhaps sometimes do, impart characteristics to the germ-cells.
“A complete and satisfactory refutation of such an opinion,” he continues, “cannot be brought forward at present”; so I suppose we must wait a little longer, but in the meantime we may again remark that, if we admit even occasional communication of changes in the somatic cells to the germ-cells, we have let in the thin end of the wedge, as Mr. Darwin did when he said that use and disuse did a good deal towards modification. Buffon, in his first volume on the lower animals, [{288}] dwells on the impossibility of stopping the breach once made by admission of variation at all. “If the point,” he writes, “were once gained, that among animals and vegetables there had been, I do not say several species, but even a single one, which had been produced in the course of direct descent from another species; if, for example, it could be once shown that the ass was but a degeneration from the horse—then there is no farther limit to be set to the power of Nature, and we should not be wrong in supposing that with sufficient time she could have evolved all other organized forms from one primordial type.” So with use and disuse and transmission of acquired characteristics generally—once show that a single structure or instinct is due to habit in preceding generations, and we can impose no limit on the results achievable by accumulation in this respect, nor shall we be wrong in conceiving it as possible that all specialization, whether of structure or instinct, may be due ultimately to habit.
How far this can be shown to be probable is, of course, another matter, but I am not immediately concerned with this; all I am concerned with now is to show that the germ-cells not unfrequently become permanently affected by events that have made a profound impression upon the somatic cells, in so far that they transmit an obvious reminiscence of the impression to the embryos which they go subsequently towards forming. This is all that is necessary for my case, and I do not find that Professor Weismann, after all, disputes it.
But here, again, comes the difficulty of saying what Professor Weismann does, and what he does not, dispute. One moment he gives all that is wanted for the Lamarckian contention, the next he denies common sense the bare necessaries of life. For a more exhaustive and detailed criticism of Professor Weismann’s position, I would refer the reader to an admirably clear article by Mr. Sidney H. Vines, which appeared in Nature, October 24, 1889. I can only say that while reading Professor Weismann’s book, I feel as I do when I read those of Mr. Darwin, and of a good many other writers on biology whom I need not name. I become like a fly in a window-pane. I see the sunshine and freedom beyond, and buzz up and down their pages, ever hopeful to get through them to the fresh air without, but ever kept back by a mysterious something, which I feel but cannot either grasp or see. It was not thus when I read Buffon, Erasmus Darwin, and Lamarck; it is not thus when I read such articles as Mr. Vines’s just referred to. Love of self-display, and the want of singleness of mind that it inevitably engenders—these, I suppose, are the sins that glaze the casements of most men’s minds; and from these, no matter how hard he tries to free himself, nor how much he despises them, who is altogether exempt?
Finally, then, when we consider the immense mass of evidence referred to briefly, but sufficiently, by Mr. Charles Darwin, and referred to without other, for the most part, than off-hand dismissal by Professor Weismann in the last of the essays that have been recently translated, I do not see how anyone who brings an unbiased mind to the question can hesitate as to the side on which the weight of testimony inclines. Professor Weismann declares that “the transmission of mutilations may be dismissed into the domain of fable.” [{290}] If so, then, whom can we trust? What is the use of science at all if the conclusions of a man as competent as I readily admit Mr. Darwin to have been, on the evidence laid before him from countless sources, is to be set aside lightly and without giving the clearest and most cogent explanation of the why and wherefore? When we see a person “ostrichizing” the evidence which he has to meet, as clearly as I believe Professor Weismann to be doing, we shall in nine cases out of ten be right in supposing that he knows the evidence to be too strong for him.