304 THE COLOURS OF AKIMAL8 



Display in courtship occurs in plainly coloured as well 

 as in ornamental species 



In speaking of the display of decorative plumage, 

 Mr. Wallace remarks : * It is very suggestive that simi- 

 lar strange movements are performed by many birds 

 which have no ornamental plumage to display.' The 

 same facts are probably true of all groups of animals 

 in which the males of certain species are specially 

 adorned. It was certainly the case with spiders, and 

 the ' assembling ' of the males of the sombre Antler 

 Moth has been already described. 



The great beauty of many appearances which are, 

 nevertheless, of extreme importance as Protective 

 Eesemblances, is doubtless explicable in the same 

 manner. It is likely that all visible parts of the 

 organism, even those with a definite physiological 

 meaning, appeal to the aesthetic sense of the opposite 

 sex. The harsh contrasts and gaudy colours of warn- 

 ing appearances, and the sombre tints which bring 

 perfect concealment, must alike possess a meaning in 

 courtship, but the tendency towards the develop- 

 ment of higher forms of beauty is rigorously kept 

 in check by natural selection. Eemove the check or 

 render it less exacting, and the tendency at once 

 manifests itself (see pp. 311-13). 



