uld possess webbed feet; that a thrush-like bird should dive and feed
on sub-aquatic insects; and that a petrel should have the habits and
structure fitting it for the life of an auk! and so in endless other
cases. But on the view of each species constantly trying to increase in
number, with natural selection always ready to adapt the slowly varying
descendants of each to any unoccupied or ill-occupied place in nature,
these facts cease to be strange, or might even have been anticipated.

We can to a certain extent understand how it is that there is so much
beauty throughout nature; for this may be largely attributed to the
agency of selection. That beauty, according to our sense of it, is not
universal, must be admitted by every one who will look at some venomous
snakes, at some fishes, and at certain hideous bats with a distorted
resemblance to the human face. Sexual selection has given the most
brilliant colours, elegant patterns, and other ornaments to the males,
and sometimes to both sexes of many birds, butterflies and other
animals. With birds it has often rendered the voice of the male musical
to the female, as well as to our ears. Flowers and fruit have been
rendered conspicuous by brilliant colours in contrast with the green
foliage, in order that the flowers may be easily seen, visited and
fertilized by insects, and the seeds disseminated by birds. How it comes
that certain colours, sounds and forms should give pleasure to man and
the lower animals, that is, how the sense of beauty in its simplest form
was first acquired, we do not know any more than how certain odours and
flavours were first rendered agreeable.

As natural selection acts by competition, it adopts and improves the
inhabitants of each country only in relation to their co-inhabitants; so
that we need feel no surprise at the species of any one country,
although on the ordinary view supposed to have been created and
specially adapted for that country, being beaten and supplanted by the
naturalized productions from another land. Nor ought we marvel if all
the contrivances in nature be not, as far as we can judge, absolutely
perfect, as in the case even of the human eye; or if some of them be
abhorrent to our ideas of fitness. We need not marvel at the sting of
the bee, when used against an enemy, causing the bee's own death; at
drones being produced in such great numbers for one single act, and
being then slaughtered by their sterile sisters; at t