and I account partly for
their difference by partial transference of colour from the male, and by
other means too long to specify; but I earnestly wish to see reason
to believe that each is specially adapted for concealment to its
environment.

I grieve to differ from you, and it actually terrifies me and makes me
constantly distrust myself. I fear we shall never quite understand each
other. I value the cases of bright-coloured, incubating male fisher, and
brilliant female butterflies, solely as showing that one sex may be made
brilliant without any necessary transference of beauty to the other sex;
for in these cases I cannot suppose that beauty in the other sex was
checked by selection.

I fear this letter will trouble you to read it. A very short answer
about your belief in regard to the female finches and Gallinaceae would
suffice.

LETTER 450. A.R. WALLACE TO CHARLES DARWIN. 9, St. Mark's Crescent,
N.W., September 27th, 1868.

Your view seems to be that variations occurring in one sex are
transmitted either to that sex exclusively or to both sexes equally, or
more rarely partially transferred. But we have every gradation of
sexual colours, from total dissimilarity to perfect identity. If this is
explained solely by the laws of inheritance, then the colours of one or
other sex will be always (in relation to the environment) a matter of
chance. I cannot think this. I think selection more powerful than laws
of inheritance, of which it makes use, as shown by cases of two, three
or four forms of female butterflies, all of which have, I have little
doubt, been specialised for protection.

To answer your first question is most difficult, if not impossible,
because we have no sufficient evidence in individual cases of slight
sexual difference, to determine whether the male alone has acquired his
superior brightness by sexual selection, or the female been made duller
by need of protection, or whether the two causes have acted. Many of the
sexual differences of existing species may be inherited differences from
parent forms, which existed under different conditions and had greater
or less need of protection.

I think I admitted before, the general tendency (probably) of males to
acquire brighter tints. Yet this cannot be universal, for many female
birds and quadrupeds have equally bright tints.

To your second question I can reply more decidedly. I do think the
females of the Gallinaceae you mention have been mod