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 

 in a 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 avoid 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 



