subject. I confess on
receiving your note that I felt rather flat at my recent work being
almost thrown away, but I did not intend to show this feeling. As a
proof how little advance I had made on the subject, I may mention that
though I had been collecting facts on the colouring and other sexual
differences in mammals, your explanation with respect to the females had
not occurred to me. I am surprised at my own stupidity, but I have long
recognised how much clearer and deeper your insight into matters is than
mine.

I do not know how far you have attended to the laws of inheritance, so
what follows may be obvious to you. I have begun my discussion on sexual
selection by showing that new characters often appear in one sex and are
transmitted to that sex alone, and that from some unknown cause such
characters apparently appear oftener in the male than in the female.
Secondly, characters may be developed and be confined to the male, and
long afterwards be transferred to the female. Thirdly, characters may,
again, arise in either sex and be transmitted to both sexes, either in
an equal or unequal degree. In this latter case I have supposed that the
survival of the fittest has come into play with female birds and kept
the female dull-coloured. With respect to the absence of spurs in female
gallinaceous birds, I presume that they would be in the way during
incubation; at least, I have got the case of a German breed of fowls in
which the hens were spurred, and were found to disturb and break their
eggs much.

With respect to the females of deer not having horns, I presume it is to
save the loss of organised matter.

In your note you speak of sexual selection and protection as sufficient
to account for the colouring of all animals; but it seems to me doubtful
how far this will come into play with some of the lower animals, such as
sea anemones, some corals, etc. etc.

On the other hand, Haeckel has recently well shown that the transparency
and absence of colour in the lower oceanic animals, belonging to the
most different classes, may be well accounted for on the principle of
protection.

Some time or other I should like much to know where your paper on the
nests of birds has appeared, and I shall be extremely anxious to read
your paper in the _Westminster Review_.

Your paper on the sexual colouring of birds will, I have no doubt, be
very striking.

Forgive me, if you can, for a touch of illiberality about your paper