SEXUAL COLOEATION. 269 



Mr. Wallace goes on to remark " that female birds liave 

 unaccountable likes and dislikes in the matter of their partners, 

 just as we have ourselves " ; and, it may be added, just as they 

 and other animals have in the choice of their food, some eating 

 greedily creatures coloured in such a way as to cause other 

 animals to refuse them. As to sexual selection in our own 

 species, it is quite clear that a girl selects her husband, just as 

 a bird often does, because he is the first comer ; and when a 

 real selection occurs, it is by no means always beauty of body 

 or of mind that wins the day. 



Mr. Poulton, who is a strong believer in " sexual selection," 

 admits that it is " still to some extent sub judice,'' simply 

 because there is a lack of evidence from carefal watching of 

 the phenomena of courtship. 



Some Arguments in Favour of Sexual Selection. 

 Mv. Poulton supports the theory of sexual selection by 

 several very ingenious considerations. He points out that 

 " the appearance of beautiful colours and patterns, which are 

 displayed in courtship, invariably occurs in diurnal, or par- 

 tially diurnal, animals." Goatsuckers and owls undoubtedly 

 support this conclusion ; and yet the enormously elongated 

 tail of the night-jar, shown in the figure (fig. 33), might be 

 put down to sexual selection ; the day-flying moths, such 

 as the magnificent Uraniidte aud the Oastniidas, are more 

 brilliant in their coloration thau the generality of nocturnal 

 moths. Sexnal colours, moreover, " are not developed on 

 l)arts of the body which move so rapidly that they become 

 invisible." In the humming birds, for instance, it is the 

 breast which commonly shows the brilliant metallic colora- 

 tion which is so characteristic of the order, and not the 

 rapidly vibrating wings. 



