50 
NATURAL SELECTION 
til 
tions, when not accompanied by others that were unfavourable, 
would certainly survive. At one time a little step might be 
made in this direction, at another time in that — a change of 
conditions might sometimes render useless that which it had 
taken ages to produce — great and sudden physical modifica- 
tions might often produce the extinction of a race just as it 
was approaching perfection, and a hundred checks of which 
we can know nothing may have retarded the progress towards 
perfect adaptation ■ so that we can hardly wonder at there 
being so few cases in which a completely successful result has 
been attained as shown by the abundance and wide diffusion 
of the creatures so protected. 
Objection that Colour , as being dangerous, should not exist in 
Natwre 
It is as well here to reply to an objection that will no 
doubt occur to many readers — that if concealment is so useful 
to all animals, and so easily brought about by variation and 
survival of the fittest, there ought to be no conspicuously- 
coloured creatures; and they will perhaps ask how we 
account for the brilliant birds, and painted snakes, and 
gorgeous insects that occur abundantly all over the world. 
It will be advisable to answer this question rather fully, in 
order that we may be prepared to understand the phenomena 
of “ mimicry, 1 ’ which it is the special object of this chapter to 
illustrate and explain. 
The slightest observation of the life of animals will show 
us that they escape from their enemies and obtain their food 
in an infinite number of ways, and that their varied habits 
and instincts are in every case adapted to the conditions of 
their existence. The porcupine and the hedgehog have a 
defensive armour that saves them from the attacks of most 
animals. The tortoise is not injured by the conspicuous 
colours of his shell, because that shell is in most cases an 
effectual protection to him. The skunks of North America 
find safety in their power of emitting an unbearably offensive 
odour ; the beaver in its aquatic habits and solidly constructed 
abode. In some cases the chief danger to an animal occurs 
at one particular period of its existence, and if that is guarded 
against its numbers can easily be maintained. This is the 
