Chapter LIII: Part I: , pp. 20-24

[107] It will, I suppose, be said that the non-inheritance of mutilations
constitutes evidence of the kind here asked for. The first reply is
that the evidence is conflicting, as it may well be. It is forgotten
that to have valid evidence of non-inheritance of mutilations, it is
requisite that both parents shall have undergone mutilation, and that
this does not often happen. If they have not, then, assuming the
inheritableness of mutilations, there would, leaving out other
causes, be an equal tendency to appearance and non-appearance of the
mutilation in offspring. But there is another cause--the tendency to
reversion, which ever works in the direction of cancelling individual
characters by the return to ancestral characters. So that even were
the inheritance of mutilations to be expected (and for myself I may
say that its occurrence surprises me), it could not be reasonably
looked for as more than exceptional: there are two strong
countervailing tendencies. But now, in the second place, let it be
remarked that the inheritance or non-inheritance of mutilations is
beside the question. The question is whether modifications of parts
produced by modifications of functions are inheritable or not. And
then, by way of disproof of their inheritableness, we are referred to
cases in which the modifications of parts are not produced by
modifications of functions, but are otherwise produced!

[108] See _First Principles_, Part II, Chap. XXII, "Equilibration."

[109] _Principles of Biology_, § 46, (No. 8. April, 1863).

[110] _Ibid._ This must not be understood as implying that while the mass
increases as the cubes, the _quantity of motion_ which can be
generated increases only as the squares; for this would not be true.
The quantity of motion is obviously measured, not by the sectional
areas of the muscles alone, but by these multiplied into their
lengths, and therefore increases as the cubes. But this admission
leaves untouched the conclusion that the ability to _bear stress_
increases only as the squares; and thus limits the ability to
generate motion, by relative incoherence of materials.

[111] _The Transactions of the Linnæan Society of London_, Vol. XXII, p.
215. The estimate of Reaumur, cited by Kirby and Spence, is still
higher--"in five generations one Aphis may be the progenitor of
5,904,900,000 descendants; and that it is supposed that in one year
there may be twenty generations." (_Introduction to Entomology_, Vol.
I, p. 175)

[112] _A Manual of the Anatomy of Invertebrated Animals_, by T. H. Huxley,
p. 206.

[113] Respecting the _Eloidea_ I learn that in 1879--thirty years after it
had become a pest--one solitary male plant was found in a pond near
Edinburgh; but "in an exhaustive inquiry on the plant made by Dr.
Groenland, of Copenhagen, he could find no trace of any male
specimens having been found in Europe other than the Scotch." In
waters from which the _Eloidea_ has disappeared, it seems to have
done so in consequence of the growth of an _Alga_, which has produced
turbid water unfavourable to it. That is to say, the decreased
multiplication of somatic cells in some cases, is not due to any
exhaustion, but is caused by the rise of enemies or adverse
conditions; as happens generally with introduced species of plants
and animals which multiply at first enormously, and then, without any
loss of reproductive power, begin to decrease under the antagonizing
influences which grow up.

[114] _A Text Book of Human Physiology._ By Austin Flint, M.D., LL.D.
Fourth edition. New York: D. Appleton & Co. 1888. Page 797.

[115] This supposition I find verified by Mr. A. S. Packard in his
elaborate monograph on "The Cave Fauna of North America, &c.," as
also in his article published in the _American Naturalist_,
September, 1888; for he there mentions "variations in _Pseudotremia
cavernarum_ and _Tomocerus plumbeus_, found living near the entrance
to caves in partial daylight." The facts, as accumulated by Mr.
Packard, furnished a much more complete answer to Prof. Lankester
than is above given, as, for example, the "blindness of _Neotoma_, or
the Wood-Rat of Mammoth Cave." It seems that there are also "cave
beetles, with or without rudimentary eyes," and "eyeless spiders" and
Myriapods. And there are insects, as some "species of Anophthalmus
and Adelops, whose larvæ are lacking in all traces of eyes and optic
nerves and lobes." These instances cannot be explained as sequences
of an inrush of water carrying with it the remote ancestors, some of
which did not find their way out; nor can others of them be explained
by supposing an inrush of air, which did the like.

[116] See "Social Organism" in _Westminster Review_ for January, 1860; also
_Principles of Sociology_, § 247.

[117] _Contemporary Review_, September, 1893.

[118] _Evolution of Sex_, p. 50.

[119] _Souvenirs Entomologiques_, 3^{me} Série, p. 328.

[120] _Natural History of Bees_, new ed., p. 33.

[121] _Origin of Species_, 6th ed., p. 232.

[122] _Contemporary Review_, September, 1893, p. 333.

[123] _The Entomologist's Monthly Magazine_, March, 1892, p. 61.

[124] Perhaps it will be alleged that nerve-matter is costly, and that this
minute economy might be of importance. Anyone who thinks this will no
longer think it after contemplating a litter of half-a-dozen young
rabbits (in the wild rabbit the number varies from four to eight);
and on remembering that the nerve-matter contained in their brains
and spinal cords, as well as the materials for building up the bones,
muscles, and viscera of their bodies, has been supplied by the doe in
the space of a month; at the same time that she has sustained herself
and carried on her activities: all this being done on relatively poor
food. Nerve-matter cannot be so very costly then.

[125] _Loc. cit._, p. 318.

[126] _The Germ Plasm_, p. 54.

[127] While Professor Weismann has not dealt with my argument derived from
the distribution of discriminativeness on the skin, it has been
criticized by Mr. McKeen Cattell, in the last number of _Mind_
(October, 1893). His general argument, vitiated by extreme
misconceptions, I need not deal with. He says:--"Whether changes
acquired by the individual are hereditary, and if so to what extent,
is a question of great interest for ethics no less than for biology.
But Mr. Spencer's application of this doctrine to account for the
origin of species [!] simply begs the question. He assumes useful
variations [!]--whether of structure or habit is immaterial--without
attempting to explain their origin": two absolute misstatements in
two sentences! The only part of Mr. Cattell's criticism requiring
reply is that which concerns the "sensation-areas" on the skin. He
implies that since Weber, experimental psychologists have practically
set aside the theory of sensation areas: showing, among other things,
that relatively great accuracy of discrimination can be quickly
acquired by "increased interest and attention.... Practice for a few
minutes will double the accuracy of discrimination, and practice on
one side of the body is carried over to the other." To me it seems
manifest that "increased interest and attention" will not enable a
patient to discriminate two points where a few minutes before he
could perceive only one. That which he can really do in this short
time is to learn to discriminate between the _massiveness of a
sensation_ produced by two points and the massiveness of that
produced by one, and to _infer_ one point or two points accordingly.
Respecting the existence of sensation-areas marked off from one
another, I may, in the first place, remark that since the eye
originates as a dermal sac, and since its retina is a highly
developed part of the sensitive surface at large, and since the
discriminative power of the retina depends on the division of it into
numerous rods and cones, each of which gives a separate
sensation-area, it would be strange were the discriminative power of
the skin at large achieved by mechanism fundamentally different. In
the second place I may remark that if Mr. Cattell will refer to
Professor Gustav Retzius's _Biologische Untersuchungen_, New Series,
vol. iv (Stockholm, 1892), he will see elaborate diagrams of
superficial nerve-endings in various animals showing many degrees of
separateness. I guarded myself against being supposed to think that
the sensation-areas are sharply marked off from one another; and
suggested, contrariwise, that probably the branching
nerve-terminations intruded among the branches of adjacent
nerve-terminations. Here let me add that the intrusion may vary
greatly in extent; and that where the intruding fibres run far among
those of adjacent areas, the discriminativeness will be but small,
while it will be great in proportion as each set of branching fibres
is restricted more nearly to its own area. All the facts are
explicable on this supposition.

[128] To save space and exclude needless complication I have omitted these
passages from the preceding divisions of this appendix.

[129] Though Professor Weismann does not take up the challenge, Dr. Romanes
does. He says:--"When selection is withdrawn there will be no
excessive _plus_ variations, because so long as selection was present
the efficiency of the organ was maintained at its highest level: it
was only the _minus_ variations which were then eliminated"
(_Contemporary Review_, p. 611). In the first place, it seems to me
that the phrases used in this sentence beg the question. It says that
"the efficiency of the organ was maintained at its _highest_ level";
which implies that the highest level (tacitly identified with the
greatest size) is the best and that the tendency is to fall below it.
This is the very thing I ask proof of. Suppose I invert the idea and
say that the organ is maintained at its right size by natural
selection, because this prevents increase beyond the size which is
best for the organism. Every organ should be in due proportion, and
the welfare of the creature as a whole is interfered with by excess
as well as by defect. It may be directly interfered with--as for
instance by too big an eyelid; and it may be indirectly interfered
with, where the organ is large, by needless weight and cost of
nutrition. In the second place the question which here concerns us is
not what natural selection will do with variations. We are concerned
with the previous question--What variations will arise? An organ
varies in all ways; and, unless reason to the contrary is shown, the
assumption must be that variations in the direction of increase are
as frequent and as great as those in the direction of decrease. Take
the case of the tongue. Certainly there are tongues inconveniently
large, and probably tongues inconveniently small. What reason have we
for assuming that the inconveniently small tongues occur more
frequently than the inconveniently large ones? None that I can see.
Dr. Romanes has not shown that when natural selection ceases to act
on an organ the _minus_ variations in each new generation will exceed
the _plus_ variations. But if they are equal the alleged process of
panmixia has no place.

[130] _The Variation of Animals and Plants under Domestication_, vol. ii,
p. 292.

[131] _Journal of the Anthropological Institute_ for 1885, p. 253.

[132] In "The All-Sufficiency of Natural Selection" (_Contemporary Review_,
Sept., 1893, p. 311), Professor Weismann writes:--"I have ever
contended that the acceptance of a principle of explanation is
justified, if it can be shown that without it certain facts are
inexplicable." Unless, then, Prof. Weismann can show that the
distribution of discriminativeness is otherwise explicable, he is
bound to accept the explanation I have given, and admit the
inheritance of acquired characters.

[133] Prof. Weismann is unaware that the view here ascribed to Roux,
writing in 1881, is of far earlier date. In the _Westminster Review_
for January, 1860, in an essay on "The Social Organism," I
wrote:--"One more parallelism to be here noted, is that the different
parts of a social organism, like the different parts of an individual
organism, compete for nutriment; and severally obtain more or less of
it according as they are discharging more or less duty." (See also
_Essays_, i, 290.) And then, in 1876, in _The Principles of
Sociology_, vol. i, § 247, I amplified the statement thus:--"All
other organs, therefore, jointly and individually, compete for blood
with each organ ... local tissue-formation (which under normal
conditions measures the waste of tissue in discharging function) is
itself a cause of increased supply of materials ... the resulting
competition, not between units simply, but between organs, causes in
a society, as in a living body, high nutrition and growth of parts
called into greatest activity by the requirements of the rest."
Though I did not use the imposing phrase
"intra-individual-selection," the process described is the same.

[134] _Proceedings of the Biological Society of Washington_, vol. ix.

[135] Romanes Lecture, p. 29.

[136] _Ibid._, p. 35.

[137] This interpretation harmonizes with a fact which I learn from Prof.
Riley, that there are gradations in this development, and that in
some species the ordinary neuters swell their abdomens so greatly
with food that they can hardly get home.