88 NATURAL SELECTION Ill 
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 dis- 
guise, 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 account- 
ing for the protective tints of arctic and desert animals. 
But this being granted, there is such a perfectly continuous 
and graduated series of examples of every kind of protective 
imitation, up to the most wonderful cases of what is termed 
“mimicry,” that we can find no place at which to draw the 
line, and-say: So far variation and natural selection will 
account for the phenomena, but for all the rest we require a 
more potent cause. The counter theories that have been 
proposed, that of the “special creation” of each imitative 
form, that of the action of “similar conditions of existence” 
for some of the cases, and of the laws of “hereditary descent 
and the reversion to ancestral forms” for others,—have all 
been shown to be beset with difficulties, and the two latter 
to be directly contradicted by some of the most constant and 
most remarkable of the facts to be accounted for. 
General deductions as to Colour in Nature 
The important part that “protective resemblance” has 
played in determining the colours and markings of many 
groups of animals, will enable us to understand the meaning 
of one of the most striking facts in nature, the uniformity in 
