RESEMBLANCES AMONG ANIMALS, 125 
another group; and we know that the creatures re- 
sembled, possess an immunity from attack, by their 
being always very abundant, by their being conspi- 
cuous 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 in- 
crease. 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 
