"If, for instance, it could be shown that artificial mutilation
spontaneously reappears in the offspring with sufficient frequency to
exclude all possibilities of chance, then such proof [_i.e._, that
acquired characters can be transmitted] would be forthcoming. The
transmission of mutilations has been frequently asserted, and has been
even recently again brought forward, but all the supposed instances have
broken down when carefully examined" (p. 390).
Here, then, we are told that proof of the occasional transmission of
mutilations would be sufficient to establish the fact, but on p. 267 we
find that no single fact is known which really proves that acquired
characters can be transmitted, "_for the ascertained facts which seem to
point to the transmission of artificially produced diseases cannot be
considered as proof_" [Italics mine.] Perhaps; but it was mutilation in
many cases that Professor Weismann practically admitted to have been
transmitted when he declared that Obersteiner had verified
Brown-Sequard's experiments.
That Professor Weismann recognises the vital importance to his own theory
of the question whether or no mutilations can be transmitted under any
circumstances, is evident from a passage on p. 425 of his work, on which
he says: "It can hardly be doubted that mutilations are acquired
characters; they do not arise from any tendency contained in the germ,
but are merely the reaction of the body under certain external
influences. They are, as I have recently expressed it, purely
somatogenic characters--viz., characters which emanate from the body
(_soma_) only, as opposed to the germ-cells; they are, therefore,
characters that do not arise from the germ itself.
"If mutilations must necessarily be transmitted" [which no one that I
know of has maintained], "or even if they might occasionally be
transmitted" [which cannot, I imagine, be reasonably questioned], "a
powerful support would be given to the Lamarckian principle, and the
transmission of functional hypertrophy or atrophy would thus become
highly probable."
I have not found any further attempt in Professor Weismann's book to deal
with the evidence adduced by Mr. Darwin to show that mutilations, if
followed by diseases, are sometimes inherited; and I must leave it to the
reader to determine how far Professor Weismann has shown reason for
rejecting Mr. Darwin's conclusion. I do not, however, dwell upon these
facts now as evidence of a transmitted change of bodily form, or of
instinct due to use and disuse or habit; what they prove is that the germ-
cells within the parent's body do not stand apart from the other cells of
the body so completely as Professor Weismann would have us believe, but
that, as Professor Hering, of Prague, has aptly said, they echo with more
or less frequency and force to the profounder impressions made upon other
cells.
I may say that Professor Weismann does not more cavalierly wave aside the
mass of evidence collected by Mr. Darwin and a host of other writers, to
the effect that mutilations are sometimes inherited, than does Mr.
Wallace, who says that, "as regards mutilations, it is generally admitted
that they are not inherited, and there is ample evidence on this point."
It is indeed generally admitted that mutilations, when not followed by
disease, are very rarely, if ever, inherited; and Mr. Wallace's appeal to
the "ample evidence" which he alleges to exist on this head, is much as
though he should say that there is ample evidence to show that the days
are longer in summer than in winter. "Nevertheless," he continues, "a
few cases of apparent inheritance of mutilations have been recorded, and
these, if trustworthy, are difficulties in the way of the theory." . . .
"The often-quoted case of a disease induced by mutilation being inherited
(Brown-Sequard's epileptic guinea-pigs) has been discussed by Professor
Weismann and shown to be not conclusive. The mutilation itself--a
section of certain nerves--was never inherited, but the resulting
epilepsy, or a general state of weakness, deformity, or sores, was
sometimes inherited. It is, however, possible that the mere injury
introduced and encouraged the growth of certain microbes, which,
spreading through the organism, sometimes reached the germ-cells, and
thus transmitted a diseased condition to the offspring." {35}
I suppose a microbe which made guinea-pigs eat their toes off was
communicated to the germ-cells of an unfortunate guinea-pig which had
been already microbed by it, and made the offspring bite its toes off
too. The microbe has a good deal to answer for.
On the case of the deterioration of horses in the Falkland Islands after
a few generations, Professor Weismann says:--
"In such a case we have only to assume that the climate which is
unfavourable, and the 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," {36} 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, {37}
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 organised 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
specialisation, 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 any one 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." {38} 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 "ostrichising" 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.