tting bird exposed to view."
At this time Mr. Wallace allowed considerably more influence to sexual
selection (in combination with the need of protection) than in his later
writings. The following extract from a letter from Mr. Wallace to Darwin
(July 23rd, 1877) fixes the period at which the change in his views
occurred: "I am almost afraid to tell you that in going over the subject
of the colours of animals, etc., etc., for a small volume of essays,
etc., I am preparing, I have come to conclusions directly opposed to
voluntary sexual selection, and believe that I can explain (in a general
way) all the phenomena of sexual ornaments and colours by laws of
development aided by simple 'Natural Selection.'" He finally rejected
Mr. Darwin's theory that colours "have been developed by the preference
of the females, the more ornamented males becoming the parents of each
successive generation." "Darwinism," 1889, page 285. See also Letters
442, 443, 449, 450, etc.)

Down, April 15th, [1868].

I have been deeply interested by your admirable article on birds' nests.
I am delighted to see that we really differ very little,--not more than
two men almost always will. You do not lay much or any stress on new
characters spontaneously appearing in one sex (generally the male), and
being transmitted exclusively, or more commonly only in excess, to that
sex. I, on the other hand, formerly paid far too little attention to
protection. I had only a glimpse of the truth; but even now I do not
go quite as far as you. I cannot avoid thinking rather more than you
do about the exceptions in nesting to the rule, especially the partial
exceptions, i.e., when there is some little difference between the sexes
in species which build concealed nests. I am not quite satisfied about
the incubating males; there is so little difference in conspicuousness
between the sexes. I wish with all my heart I could go the whole length
with you. You seem to think that male birds probably select the most
beautiful females; I must feel some doubt on this head, for I can find
no evidence of it. Though I am writing so carping a note, I admire the
article thoroughly.

And now I want to ask a question. When female butterflies are more
brilliant than their males you believe that they have in most cases, or
in all cases, been rendered brilliant so as to mimic some other species,
and thus escape danger. But can you account for the males not having
been rendered equally b