Chap. XVI.] SUMMARY. - 223 



the most brilliant tints, combs and wattles, beautiful 

 plumes, elongated feathers, top-knots, and so forth, are by 

 far the commonest means. In some cases mere novelty 

 appears to have acted as a charm. The ornaments of the 

 males must be highly important to them, for they have 

 been acquired in not a few cases at the cost of increased 

 danger from enemies, and even at some loss of power in 

 fighting with their rivals. The males of very many spe- 

 cies do not assume their ornamental dress until they ar- 

 rive at maturity, or they assume it only during the breed- 

 ing-season, or the tints then become more vivid. Certain 

 ornamental appendages become enlarged, turgid, and 

 bright-colored, during the very act of courtship. The 

 males display their charms with elaborate care and to the 

 best effect ; and this is done in the presence of the females. 

 The courtship is sometimes a prolonged affiiir, and many 

 males and females congregate at an appointed place. To 

 suppose that the females do not appreciate the beauty of 

 the males is to admit that their splendid decorations, all 

 their pomp and display, are useless ; and this is incredible. 

 Birds have fine powers of discrimination, and in some few 

 instances it can be shown that they have a taste for the 

 beautiful. The females, moreover, are known occasionally 

 to exhibit a marked preference or antipathy for cei'tain in- 

 dividual males. 



If it be admitted that the females prefer, or are uncon- 

 sciously excited by, the more beautiful males, then the 

 males would slowly but surely be rendered more and more 

 attractive through sexual selection. That it is this sex 

 which has been chiefly modified we may infer from the 

 fact that in almost every genus in which the sexes differ, 

 the males differ much more from each other than do the 

 females ; this is well shown in certain closely-allied repre- 

 sentative species in which the females can hardly be dis- 

 tinguished, while the males are quite distinct. Birds in a 



