into the subject, and cannot say that I am fully satisfied. I remember
mentioning to you the case of Rhynchoea, but its nesting seems unknown. In
some other cases the difference in brightness seemed to me hardly
sufficiently accounted for by the principle of protection. At the Falkland
Islands there is a carrion hawk in which the female (as I ascertained by
dissection) is the brightest coloured, and I doubt whether protection will
here apply; but I wrote several months ago to the Falklands to make
enquiries. The conclusion to which I have been leaning is that in some of
these abnormal cases the colour happened to vary in the female alone, and
was transmitted to females alone, and that her variations have been
selected through the admiration of the male.

It is a very interesting subject, but I shall not be able to go on with it
for the next five or six months, as I am fully employed in correcting dull
proof-sheets. When I return to the work I shall find it much better done
by you than I could have succeeded in doing.

It is curious how we hit on the same ideas. I have endeavoured to show in
my MS. discussion that nearly the same principles account for young birds
not being gaily coloured in many cases, but this is too complex a point for
a note.

On reading over your letter again, and on further reflection, I do not
think (as far as I remember my words) that I expressed myself nearly
strongly enough on the value and beauty of your generalisation (429/4. See
Letter 203, Volume I.), viz., that all birds in which the female is
conspicuously or brightly coloured build in holes or under domes. I
thought that this was the explanation in many, perhaps most cases, but do
not think I should ever have extended my view to your generalisation.
Forgive me troubling you with this P.S.