318 Darwin, and after Darwin. 
duced differs in different animals; but it is needless 
for our purposes to go into this part of the subject. 
Again, there are yet other cases where protective 
colouring which is admirably suited to conceal an 
animal through one part of the year, would become 
highly conspicuous during another part of it— namely, 
when the ground is covered with snow. Accordingly, 
in these cases the animals change their colour in the 
winter months to a snowy white: witness stoats, 
mountain hares, ptarmigan, &c. (Fig. 108.) 
Now, it is sufficiently obvious that in all these 
classes of cases the concealment from enemics or 
prey which is thus secured is of advantage to the 
animals concerned ; and, thercfore that in the theory 
of, natural selection we have a satisfactory theory 
whereby to explain it. And this cannot be said of 
any other theory of adaptive mechanisms in nature 
that has ever been propounded. The so-called La- 
marckian theory, for instance, cannot be brought to 
bear upon the facts at all; and on the theory of 
special creation it is unintelligible why the phenomena 
of protective colouring should be of such general 
occurrence. For, in as far as protective colouring 
is of advantage to the species which present it, it is 
of corresponding disadvantage to those other species 
against the predatory nature of which it acts as a 
defence And, of course, the same applics to yet 
other species, if they serve as prey. Moreover, the 
more minutely this subject is invest’'gated in all its 
details, the more exactly is it found to harmonise 
with the naturalistic interpretation 1}. 
1 Were it not that some of Darwin’s critics have overlooked the very 
point wherein the great value of protective colouring as evidence of 
