10 ANIMAL COLORATION. 



there is, of course, no gainsaying such an argument. But 

 many instances of coloration are not believed by any one to be 

 adaptive; "there can be no question of adaptation," remarks 

 Mr. Wallace, " in the brilliant colours of red snow and other low 

 jilgas and fungi, or even in the universal mantle of green which 

 clothes so large a portion of the earth's surface/' * Mr. Wallace 

 goes on to remark that "it is the wonderful individuality 

 of the colours of animals and plants that attracts our attention 

 -the fact that the colours are localised in definite patterns 

 sometimes in accordance with structural characters, sometimes 

 altogether independent of them, while often differing in the 

 most striking and fantastic manner in allied species. We are 

 thus compelled to look upon colour not merely as a physical but 

 also as a biological characteristic, which has been differentiated 

 and specialised by natural selection, and must therefore find its 

 explanation in the principle of adaptation or utility." There 

 are some cases of internal coloration which show precisely 

 the same individuality, and would, were they external, be put 

 down as colour modifications requiring some explanation on the 

 principle of utility. 



The body cavity of some lizards is deep black; the pig- 

 mentation does not affect the entire lining of the body cavity, 

 but only a part of it which is sharply differentiated from the 

 rest ; the palate of the orang-outan is black, that of the 

 chimpanzee, flesh-coloured, with no pigment at all. It is exactly 

 these specific or generic differences in coloration which are 

 sought to be explained by natural selection ; though it is clear 

 that in these instances no such explanation is possible. It 

 would not be, therefore, unreasonable to say that many forms 

 of external colour modifications may possibly be also without 

 any such explanation. It is at least too much to assume that 



* '-Darwinism,'' p. 189. 



