RESEMBLANCES AMONG ANIMALS, . 65 
most minute examination that I could convince myself 
it was not so. 
We need not adduce any more examples to show 
how important are the details of form and of colouring 
in animals, and that their very existence may often 
depend upon their being by these means concealed from 
their enemies. This kind of protection is found appar- 
ently in every class and order, for it has been noticed 
wherever we can obtain sufficient knowledge of the 
details of an animal’s life-history. It varies in degree, 
from the mere absence of conspicuous colour or a 
general harmony with the prevailing tints of nature, 
up to such a minute and detailed resemblance to inor- 
ganic or vegetable structures as to realize the talisman 
of the fairy tale, and to give its possessor the power of 
rendering itself invisible. 
Theory of Protective Colouring. 
We will now endeavour to show how these wonderful 
resemblances have most probably been brought about. 
Returning to the higher animals, let us consider the 
remarkable fact of the rarity of white colouring in the 
mammalia or birds of the temperate or tropical zones 
ina state of nature. There is not a single white land- 
bird or quadruped in Europe, except the few arctic or 
alpine species, to which white is a protective colour. 
Yet in many of these creatures there seems to be no 
inherent tendency to aveid white, for directly they are 
domesticated white varieties arise, and appear to thrive 
as well as others. We have white mice and rats, white 
F 
