modified to bring the female into harmony with the environment. "Sexual
selection is less rigorous than Natural Selection," and will therefore be
subordinate to it.

I think the case of female Pieris pyrrha proves that females alone can be
greatly modified for protection. (450/1. My latest views on this subject,
with many new facts and arguments, will be found in the later editions of
my "Darwinism," Chapter X. (A.R.W.))


LETTER 451. A.R. WALLACE TO CHARLES DARWIN.

(451/1. On October 4th, 1868, Mr. Wallace wrote again on the same subject
without adding anything of importance to his arguments of September 27th.
We give his final remarks:--)

October 4th, 1868.

I am sorry to find that our difference of opinion on this point is a source
of anxiety to you. Pray do not let it be so. The truth will come out at
last, and our difference may be the means of setting others to work who may
set us both right. After all, this question is only an episode (though an
important one) in the great question of the "Origin of Species," and
whether you or I are right will not at all affect the main doctrine--that
is one comfort.

I hope you will publish your treatise on "Sexual Selection" as a separate
book as soon as possible; and then, while you are going on with your other
work, there will no doubt be found some one to battle with me over your
facts on this hard problem.