216 MY SOMALI BOOK 



It is this : " That in addition to the influence exerted 

 in the evohition of colour in living organisms by the 

 action of sexual selection, and the necessity for pro- 

 tection against enemies, a third factor has been at work 

 which I will call the influence of environment." In 

 explanation of this last influence he expresses the 

 belief that there is "a law which, working through 

 the ages, tends to bring the colours of all organic 

 beings into harmony with their surroundings, irre- 

 spective of any special benefit they may receive in the 

 way of protection from enemies by such harmonious 

 colouration." 



If, as seems to be implied throughout his argument, 

 colouration in harmony with its surroundings means, 

 or at least involves, a measure of inconspicuousness, 

 how are we to explain the conspicuous colouring which 

 he asserts to be characteristic of the zebra and other 

 animals ? But we may let that pass. The vital 

 objection to this environment theory as presented by 

 Mr. Selous lies in the fact that it is based on a mis- 

 conception of the nature of the theory of protective 

 colouration produced by natural selection. For when 

 he speaks of the necessity for protection and the 

 influence of environment as separate factors in the 

 evolution of colouring, he can only mean that they work 

 independently. Whereas (assuming the influence of 

 environment on colour to be a fact) these two factors 

 are really complementary to each other. 



The existence of a necessity for protection can of 

 itself achieve nothing. But when by the influence of 

 environment or any other cause, a colour variation 

 appears which has some protective effect and is 



