ldish.

I am sadly over-worked, so will not write to you. I have worked in
a number of your invaluable corrections--indeed, all as far as time
permits. I infer from a letter from Huxley that Ramsay (91/2. See a
letter to Huxley, November 27th, 1859, "Life and Letters," II., page
282.) is a convert, and I am extremely glad to get pure geologists, as
they will be very few. Many thanks for your very pleasant note. What
pleasure you have given me. I believe I should have been miserable had
it not been for you and a few others, for I hear threatening of attacks
which I daresay will be severe enough. But I am sure that I can now bear
them.

LETTER 92. TO T.H. HUXLEY.

(92/1. The point here discussed is one to which Mr. Huxley attached
great, in our opinion too great, importance.)

Down, January 11th [1860?].

I fully agree that the difficulty is great, and might be made much of by
a mere advocate. Will you oblige me by reading again slowly from pages
267 to 272. (92/2. The reference is to the "Origin," Edition I.: the
section on "The Fertility of Varieties when crossed, and of their
Mongrel Offspring" occupies pages 267-72.) I may add to what is there
said, that it seems to me quite hopeless to attempt to explain why
varieties are not sterile, until we know the precise cause of sterility
in species.

Reflect for a moment on how small and on what very peculiar causes the
unequal reciprocity of fertility in the same two species must depend.
Reflect on the curious case of species more fertile with foreign pollen
than their own. Reflect on many cases which could be given, and shall
be given in my larger book (independently of hybridity) of very slight
changes of conditions causing one species to be quite sterile and not
affecting a closely allied species. How profoundly ignorant we are on
the intimate relation between conditions of life and impaired fertility
in pure species!

The only point which I might add to my short discussion on this subject,
is that I think it probable that the want of adaptation to uniform
conditions of life in our domestic varieties has played an important
part in preventing their acquiring sterility when crossed. For the want
of uniformity, and changes in the conditions of life, seem the
only cause of the elimination of sterility (when crossed) under
domestication. (92/3. The meaning which we attach to this obscure
sentence is as follows: Species in a state of nature are closely adapted
to d