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sterility:--
"When writing my "Darwinism," and coming again to the consideration
of this problem of the effect of Natural Selection in accumulating
variations in the amount of sterility between varieties or incipient
species twenty years later, I became more convinced, than I was when
discussing with Darwin, of the substantial accuracy of my argument.
Recently a correspondent who is both a naturalist and a mathematician
has pointed out to me a slight error in my calculation at page 183
(which does not, however, materially affect the result), disproving the
'physiological selection' of the late Dr. Romanes, but he can see no
fallacy in my argument as to the power of Natural Selection to increase
sterility between incipient species, nor, so far as I am aware, has any
one shown such fallacy to exist.
"On the other points on which I differed from Mr. Darwin in the
foregoing discussion--the effect of high fertility on population of a
species, etc.--I still hold the views I then expressed, but it would be
out of place to attempt to justify them here."
A.R.W. (1899).)
LETTER 217. TO C. LYELL. Down, October 4th [1867].
With respect to the points in your note, I may sometimes have expressed
myself with ambiguity. At the end of Chapter XXIII., where I say that
marked races are not often (you omit "often") produced by changed
conditions (217/1. "Hence, although it must be admitted that new
conditions of life do sometimes definitely affect organic beings, it
may be doubted whether well-marked races have often been produced by the
direct action of changed conditions without the aid of selection either
by man or nature." ("Animals and Plants," Volume II., page 292, 1868.)),
I intended to refer to the direct action of such conditions in causing
variation, and not as leading to the preservation or destruction of
certain forms. There is as wide a difference in these two respects
as between voluntary selection by man and the causes which induce
variability. I have somewhere in my book referred to the close
connection between Natural Selection and the action of external
conditions in the sense which you specify in your note. And in this
sense all Natural Selection may be said to depend on changed conditions.
In the "Origin" I think I have underrated (and from the cause which
you mention) the effects of the direct action of external conditions in
producing varieties; but I hope in Chapter XXIII. I have struck as fair
a balance as our knowledge permits.
It is wonderful to me that you have patience to read my slips, and I
cannot but regret, as they are so imperfect; they must, I think, give
you a wrong impression, and had I sternly refused, you would perhaps
have thought better of my book. Every single slip is greatly altered,
and I hope improved.
With respect to the human ovule, I cannot find dimensions given, though
I have often seen the statement. My impression is that it would be just
or barely visible if placed on a clear piece of glass. Huxley could
answer your question at once.
I have not been well of late, and have made slow progress, but I think
my book will be finished by the middle of November.
LETTER 218. A.R. WALLACE TO CHARLES DARWIN. [End of February, 1868]
I am in the second volume of your book, and I have been astonished at
the immense number of interesting facts you have brought together. I
read the chapter on pangenesis first, for I could not wait. I can hardly
tell you how much I admire it. It is a positive comfort to me to have
any feasible explanation of a difficulty that has always been haunting
me, and I shall never be able to give it up till a better one supplies
its place,--and that I think hardly possible. You have now fairly beaten
Spencer on his own ground, for he really offered no solution of the
difficulties of the problem. The incomprehensible minuteness and vast
numbers of the physiological germs or atoms (which themselves must be
compounded of numbers of Spencer's physiological units) is the only
difficulty; but that is only on a par with the difficulties in all
conceptions of matter, space, motion, force, etc.
As I understood Spencer, his physiological units were identical
throughout each species, but slightly different in each different
species; but no attempt was made to show how the identical form of the
parent or ancestors came to be built up of such units.
LETTER 219. TO A.R. WALLACE. Down, February 27th [1868].
You cannot well imagine how much I have been pleased by what you say
about pangenesis. None of my friends will speak out, except to a certain
extent Sir H. Holland, who found it very tough reading, but admits that
some view "closely akin to it" will have to be admitted. Hooker, as far
as I understand him, which I hardly do at present, seems to think that
the hypothesis is little more than saying that organisms have such
and such potentialities. What you say exactly and fully expresses my
feelings--viz., that it is a relief to have some feasible explanation
of the various facts, which can be given up as soon as any better
hypothesis is found. It has certainly been an immense relief to my mind;
for I have been stumbling over the subject for years, dimly seeing that
some relation existed between the various classes of facts. I now hear
from H. Spencer that his views quoted in my footnote refer to something
quite distinct, as you seem to have perceived. (219/1. This letter is
published in "Life and Letters," III., page 79.)
LETTER 220. A.R. WALLACE TO CHARLES DARWIN. Hurstpierpoint, March 1st,
1868.
...Sir C. Lyell spoke to me as if he has greatly admired pangenesis. I
am very glad H. Spencer at once acknowledges that his view was something
quite distinct from yours. Although, as you know, I am a great admirer
of his, I feel how completely his view failed to go to the root of the
matter, as yours does. His explained nothing, though he was evidently
struggling hard to find an explanation. Yours, as far as I can see,
explains everything in growth and reproduction--though, of course, the
mystery of life and consciousness remains as great as ever.
Parts of the chapter on pangenesis I found hard reading, and have not
quite mastered yet, and there are also throughout the discussions in
Volume II. many bits of hard reading, on minute points which we, who
have not worked experimentally at cultivation and crossing, as you have
done, can hardly see the importance of, or their bearing on the general
question.
If I am asked, I may perhaps write an article on the book for some
periodical, and, if so, shall do what I can to make "Pangenesis"
appreciated...
(220/1. In "Nature," May 25th, 1871, page 69, appeared a letter on
pangenesis from Mr. A.C. Ranyard, dealing with the difficulty that the
"sexual elements produced upon the scion" have not been shown to be
affected by the stock. Mr. Darwin, in an annotated copy of this letter,
disputes the accuracy of the statement, but adds: "THE BEST OBJECTION
YET RAISED." He seems no |