us then consider what we are to do with this
unexpected set of correspondences between groups of phenomena which, at
first sight, appear so disconnected. Do they fall in with any other
groups of natural phenomena? Do they teach us anything of the way in
which nature works, and give us any insight into the causes which have
brought about the marvellous variety, and beauty, and harmony of living
things? I believe we can answer these questions in the affirmative; and
I may mention, as a sufficient proof that these are not isolated facts,
that I was first led to see their relation to each other by the study of
an analogous though distinct set of phenomena among insects, that of
protective resemblance and "mimicry."

On considering this remarkable series of corresponding facts, the first
thing we are taught by them seems to be, that there is no incapacity in
the female sex among birds, to receive the same bright hues and strongly
contrasted tints with which their partners are so often decorated, since
whenever they are _protected and concealed_ during the period of
incubation _they are similarly adorned_. The fair inference is, that it
is chiefly due to the absence of protection or concealment during this
important epoch, that gay and conspicuous tints are withheld or left
undeveloped. The mode in which this has been effected is very
intelligible, if we admit the action of natural and sexual selection. It
would appear from the numerous cases in which both sexes are adorned
with equally brilliant colours (while both sexes are rarely armed with
equally developed offensive and defensive weapons when not required for
individual safety), that the normal action of "sexual selection" is to
develop colour and beauty in both sexes, by the preservation and
multiplication of all varieties of colour in either sex which are
pleasing to the other. Several very close observers of the habits of
animals have assured me, that male birds and quadrupeds do often take
very strong likes and dislikes to individual females, and we can hardly
believe that the one sex (the female) can have a general taste for
colour while the other has no such taste. However this may be, the fact
remains, that in a vast number of cases the female acquires as brilliant
and as varied colours as the male, and therefore most probably acquires
them in the same way as the male does; that is, either because the
colour is useful to it, or is correlated with some useful varia