be completely protected.

I think I have now noticed all exceptions of any importance to the law
of dependence of sexual colour on nidification. It will be seen that
they are very few in number, compared with those which support the
generalization; and in several cases there are circumstances in the
habits or structure of the species that sufficiently explain them. It is
remarkable also that I have found scarcely any _positive_ exceptions,
that is, cases of very brilliant or conspicuous female birds in which
the nest was not concealed. Much less can there be shown any group of
birds, in which the females are all of decidedly conspicuous colours on
the upper surface, and yet sit in open nests. The many cases in which
birds of dull colours in both sexes make domed or concealed nests, do
not, of course, affect this theory one way or the other; since its
purpose is only to account for the fact, that brilliant females of
brilliant males are _always_ found to have covered or hidden nests,
while obscure females of brilliant males _almost always_ have open and
exposed nests. The fact that all classes of nests occur with dull
coloured birds in both sexes merely shows, as I have strongly
maintained, that in most cases the character of the nest determines the
colouration of the female, and not _vice versa_.

If the views here advocated are correct, as to the various influences
that have determined the specialities of every bird's nest, and the
general colouration of female birds, with their action and reaction on
each other, we can hardly expect to find evidence more complete than
that here set forth. Nature is such a tangled web of complex relations,
that a series of correspondences running through hundreds of species,
genera, and families, in every part of the system, can hardly fail to
indicate a true casual connexion; and when, of the two factors in the
problem, one can be shown to be dependent on the most deeply seated and
the most stable facts of structure and conditions of life, while the
other is a character universally admitted to be superficial and easily
modified, there can be little doubt as to which is cause and which
effect.

_Various modes of Protection of Animals._

But the explanation of the phenomenon here attempted does not rest alone
on the facts I have been able now to adduce. In the essay on "Mimicry,"
it is shown how important a part the necessity for protection has
played, in determining the external