tiae which we should be otherwise almost sure to pass
over as insignificant or unimportant.

The adaptation of the external colouring of animals to their conditions
of life has long been recognized, and has been imputed either to an
originally created specific peculiarity, or to the direct action of
climate, soil, or food. Where the former explanation has been accepted,
it has completely checked inquiry, since we could never get any further
than the fact of the adaptation. There was nothing more to be known
about the matter. The second explanation was soon found to be quite
inadequate to deal with all the varied phases of the phenomena, and to
be contradicted by many well-known facts. For example, wild rabbits are
always of gray or brown tints well suited for concealment among grass
and fern. But when these rabbits are domesticated, without any change of
climate or food, they vary into white or black, and these varieties may
be multiplied to any extent, forming white or black races. Exactly the
same thing has occurred with pigeons; and in the case of rats and mice,
the white variety has not been shown to be at all dependent on
alteration of climate, food or other external conditions. In many cases
the wings of an insect not only assume the exact tint of the bark or
leaf it is accustomed to rest on, but the form and veining of the leaf
or the exact rugosity of the bark is imitated; and these detailed
modifications cannot be reasonably imputed to climate or food, since in
many cases the species does not feed on the substance it resembles, and
when it does, no reasonable connection can be shown to exist between the
supposed cause and the effect produced. It was reserved for the theory
of natural selection to solve all these problems, and many others which
were not at first supposed to be directly connected with them. To make
these latter intelligible, it will be necessary to give a sketch of the
whole series of phenomena which may be classed under the head of useful
or protective resemblances.

Concealment, more or less complete, is useful to many animals, and
absolutely essential to some. Those which have numerous enemies from
which they cannot escape by rapidity of motion, find safety in
concealment. Those which prey upon others must also be so constituted as
not to alarm them by their presence or their approach, or they would
soon die of hunger. Now, it is remarkable in how many cases nature gives
this boon to the anim