f material which Darwin has collected in proof
of all the points mentioned in the foregoing paragraph, that to attempt
anything in the way of an epitome would really be to damage its
evidential force. Therefore I deem it best simply to refer to it as it
stands in his _Descent of Man_, concluding, as he concludes,--"This
surprising uniformity in the laws regulating the differences between the
sexes in so many and such widely separated classes is intelligible if we
admit the action throughout all the higher divisions of the animal
kingdom of one common cause, namely, sexual selection"; while, as he
might well have added, it is difficult to imagine that all the large
classes of facts which an admission of this common cause serves to
explain, can ever admit of being rendered intelligible by any other
theory.

We may next proceed to consider the objections which have been brought
against the theory of sexual selection. And this is virtually the same
thing as saying that we may now consider Mr. Wallace's views upon the
subject.

Reserving for subsequent consideration the most general of these
objections--namely, that at best the theory can only apply to the more
intelligent animals, and so must necessarily fail to explain the
phenomena of beauty in the less intelligent, or in the non-intelligent,
as well as in all species of plants--we may take _seriatim_ the other
objections which, in the opinion of Mr. Wallace, are sufficient to
dispose of the theory even as regards the higher animals.

In the first place, he argues that the principal cause of the greater
brilliancy of male animals in general, and of male birds in particular,
is that they do not so much stand in need of protection arising from
concealment as is the case with their respective females. Consequently
natural selection is not so active in repressing brilliancy of colour in
the males, or, which amounts to the same thing, is more active in
"repressing in the female those bright colours which are normally
produced in both sexes by general laws."

Next, he argues that not only does natural selection thus exercise a
negative influence in passively permitting more heightened colour to
appear in the males, but even exercises a positive influence in actively
promoting its development in the males, while, at the same time,
actively repressing its appearance in the females. For heightened
colour, he says, is correlated with health and vigour; and as there can
be no d