Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

48 MRMICLY, AND GTIfER PROTECTIVE
to their conditions of life has long been recognisecd
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 grey 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 to food,
since in many cases the species does not feed on
the substance it resembles, and when it does, no
reasonable connexion can be shown to exist between
the supposed cause and the effect produced. It was