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

RESEMIBLANCES AMONG ANIMALS. 125
another group; and we know that the creatures resembled, possess an immunity from attack, by their
being always very abundant, by their being conspicuous and not concealing themselves, and by their
having generally no visible means of escape from
their enemies; while, at the same time, the particular
quality that makes them disliked is often very clear,
such as a nasty taste or an indigestible hardness.
Further examination reveals the fact that, in several
cases of both kinds of disguise, it is the female only
that is thus disguised; and as it can be shown that the
female needs protection much more than the male,
and that her preservation for a much longer period is
absolutely necessary for the continuance of the race,
we have an additional indication that the resemblance
is in all cases subservient to a great purpose-the
preservation of the species.
In endeavouring to explain these phenomena as
having been brought about by variation and natural
selection, we start with the fact that white varieties
frequently occur, and when protected from enemies
show no incapacity for continued existence and increase. We know, further, that varieties of many
other tints occasionally occur; and as "'the survival
of the fittest" must inevitably weed out those whose
colours are prejudicial and preserve those whose
colours are a safeguard, we require no other mode of
accounting for the protective tints of arctic and
desert animals. But this being granted, there is
such a perfectly continuous and graduated series of