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can be modified merely to favour crossing; with equal readiness it could
be modified to prevent crossing.
It is this which makes me so much interested with dimorphism, etc.
(152/2. This gives a narrow impression of Darwin's interest in
dimorphism. The importance of his work was (briefly put) the proof that
sterility has no necessary connection with specific difference, but
depends on sexual differentiation independent of racial differences. See
"Life and Letters," III., page 296. His point of view that sterility
is a selected quality is again given in a letter to Huxley ("Life and
Letters," II., page 384), but was not upheld in his later writings (see
"Origin of Species," Edition VI., page 245). The idea of sterility being
a selected quality is interesting in connection with Romanes' theory of
physiological selection. (See Letters 209-214.))
One word more. When you pitched me head over heels by your new way of
looking at the back side of variation, I received assurance and strength
by considering monsters--due to law: horribly strange as they are, the
monsters were alive till at least when born. They differ at least as
much from the parent as any one mammal from another.
I have just finished a long, weary chapter on simple facts of variation
of cultivated plants, and am now refreshing myself with a paper on Linum
for the Linnean Society.
LETTER 153. TO W.B. TEGETMEIER.
(153/1. The following letter also bears on the question of the
artificial production of sterility.)
Down, 27th [December, 1862].
The present plan is to try whether any existing breeds happen to
have acquired accidentally any degree of sterility; but to this point
hereafter. The enclosed MS. will show what I have done and know on the
subject. Please at some future time carefully return the MS. to me. If I
were going to try again, I would prefer Turbit with Carrier or Dragon.
I will suggest an analogous experiment, which I have had for two years
in my experimental book with "be sure and try," but which, as my health
gets yearly weaker and weaker and my other work increases, I suppose
I shall never try. Permit me to add that if 5 pounds would cover the
expenses of the experiment, I should be delighted to give it, and you
could publish the result if there be any result. I crossed the Spanish
cock (your bird) and white Silk hen and got plenty of eggs and chickens;
but two of them seemed to be quite sterile. I was then sadly overdone
with work, but have ever since much reproached myself that I did not
preserve and carefully test the procreative power of these hens. Now, if
you are inclined to get a Spanish cock and a couple of white Silk hens,
I shall be most grateful to hear whether the offspring breed well: they
will prove, I think, not hardy; if they should prove sterile, which I
can hardly believe, they will anyhow do for the pot. If you do try this,
how would it do to put a Silk cock to your curious silky Cochin hen, so
as to get a big silk breed; it would be curious if you could get silky
fowl with bright colours. I believe a Silk hen crossed by any other
breed never gives silky feathers. A cross from Silk cock and Cochin Silk
hen ought to give silky feathers and probably bright colours.
I have been led lately from experiments (not published) on dimorphism
to reflect much on sterility from hybridism, and partially to change
the opinion given in "Origin." I have now letters out enquiring on the
following point, implied in the experiment, which seems to me well worth
trying, but too laborious ever to be attempted. I would ask every pigeon
and fowl fancier whether they have ever observed, in the same breed, a
cock A paired to a hen B which did not produce young. Then I would get
cock A and match it to a hen of its nearest blood; and hen B to its
nearest blood. I would then match the offspring of A (viz., a, b, c, d,
e) to the offspring of B (viz., f, g, h, i, j), and all those children
which were fertile together should be destroyed until I found one--say
a, which was not quite fertile with--say, i. Then a and i should be
preserved and paired with their parents A and B, so as to try and get
two families which would not unite together; but the members WITHIN each
family being fertile together. This would probably be quite hopeless;
but he who could effect this would, I believe, solve the problem of
sterility from hybridism. If you should ever hear of individual fowls or
pigeons which are sterile together, I should be very grateful to hear of
the case. It is a parallel case to those recorded of a man not impotent
long living with a woman who remained childless; the husband died, and
the woman married again and had plenty of children. Apparently (by
no means certainly) this first man and woman were dissimilar in their
sexual organisation. I conceive it possible that their offspring
(if both had married again and both had children) would be sexually
dissimilar, like their parents, or sterile together. Pray forgive my
dreadful writing; I have been very unwell all day, and have no strength
to re-write this scrawl. I am working slowly on, and I suppose in three
or four months shall be ready.
I am sure I do not know whether any human being could understand or read
this shameful scrawl.
LETTER 154. TO T.H. HUXLEY. Down, December, 28th [1862].
I return enclosed: if you write, thank Mr. Kingsley for thinking
of letting me see the sound sense of an Eastern potentate. (154/1.
Kingsley's letter to Huxley, dated December 20th, 1862, contains a story
or parable of a heathen Khan in Tartary who was visited by a pair of
proselytising Moollahs. The first Moollah said: "Oh! Khan, worship my
God. He is so wise that he made all things." But Moollah No. 2 won the
day by pointing out that his God is "so wise that he makes all things
make themselves.") All that I said about the little book (154/2. The six
"Lectures to Working Men," published in six pamphlets and in book-form
in 1863. Mr. Huxley considered that Mr. Darwin's argument required
the production by man's selection of breeds which should be mutually
infertile, and thus resemble distinct species physiologically as well as
morphologically.) is strictly my opinion; it is in every way excellent,
and cannot fail to do good the wider it is circulated. Whether it is
worth your while to give up time to it is another question for you alone
to decide; that it will do good for the subject is beyond all question.
I do not think a dunce exists who could not understand it, and that is
a bold saying after the extent to which I have been misunderstood. I did
not understand what you required about sterility: assuredly the facts
given do not go nearly so far. We differ so much that it is no use
arguing. To get the degree of sterility you expect in recently formed
varieties seems to me simply hopeless. It seems to me almost like those
naturalists who declare they will never believe that one species turns
into another till they see eve |