4 AFRICAN NATURE NOTES CHAP. 



in which such conspicuous colours are shown, it 

 must be conceded that a coloration harmonising 

 with its surroundings is not a necessity of existence 

 in all cases to all species of mammals, birds, reptiles, 

 and insects, and that it is therefore quite possible 

 that where living organisms agree very closely in 

 colour with their surroundings, such harmonious 

 coloration may have been produced by some other 

 agency than the need for protection by colour, and 

 I would suggest that in addition to the influence 

 exerted in the evolution of colour in living organisms 

 by the action of sexual selection, and the necessity 

 for protection against enemies, a third factor has 

 also been at work, which I will call the influence 

 of environment. 



It is worthy of remark, I think, that in hot, dry 

 deserts, where the climatic conditions are stable, 

 and where the general colour of the landscape is 

 therefore very much the same all the year round, 

 all the resident species of mammals, birds, reptiles, 

 and insects are what is called protectively coloured, 

 that is to say, they are all of a dull brown or 

 greyish coloration, 1 which harmonises beautifully with 

 their parched, dull-coloured environment. In the 

 leucoryx, the Saharan representative of the gems- 

 buck of South-Western Africa, all the black mark- 

 ings which are so conspicuous in the latter animal 

 have disappeared or become pale brown, whilst the 

 general colour of the body has been bleached to a 

 dirty white. Now, no one can persuade me that 

 if the leucoryx were coloured exactly like its near 

 relative the gemsbuck, it would suffer one iota 

 more, in the open country in which it lives, from the 

 attacks of carnivorous animals than it does at 

 present, and I therefore believe that the faded 



1 The rock ostrich is, I think, the only exception to this rule, and in the 

 case of this remarkable bird the influence of sexual selection has probably 

 been more potent than that of a dull-coloured, monotonous environment. 



