Contents. xv 



CHAPTER XIV. 



Bikds — continued. 



PAOK 



Choice exerted by the female — Length of courtship — Unpaired 

 birds — Mental qualities and taste for the beautiful — Preference 

 or antipathy shewn by the female for particular males — Vari- 

 ability of birds — Variations sometimes abrupt — Laws of varia- 

 tion — Formation of ocelli — Gradations of character — Case of 

 Peacock, Argus pheasant, and Urosticte . . . 404 



CHAPTER XV. 



B irds — continued. 



Discussion as to why the males alone of some species, and both 

 sexes of others are brightly coloured — Oa sexually-limited 

 inheritance, as applied to various structures and to brightly- 

 coloured plumage — Nidification in relation to colour — Loss of 

 nuptial phnnage during the winter .... 444 



CHAPTER XVI. 



Birds — concluded. 



The immature plumage in relation to the character of the plumage 

 in both sexes when adult — Six classes of cases — Sexual differ- 

 ences between the males of closely-allied or representative 

 species — The female assuming the characters of the male — 

 Plumage of the young in relation to the summer and winter 

 plumage of the adults — On the increase of beauty in the birds 

 of the world — Protective colouring — Conspicuously-coloured 

 birds — Novelty appreciated — Summary of the four chapters on 

 birds ......... 463 



CHAPTER XVII. 



Secondary Sexual Characters of Mammals. 



The law of battle — Special weapons, confined to the males — Cause 

 of absence of weapons in the female — Weapons common to both 

 sexes, yet primarily acquired by the male — Other uses of such 

 "weapons — Their high importance — Greater size of the male — 

 Means of defence — On the preference shewn by either sex in the 

 pairing of quadrupeds ...... 501! 



CHAPTER XVIII. 



Secondary Sexual Characters of Mammals — continued, 



Voice — Remarkable sexual peculiarities in seals — Odour — Develop- 

 ment of the hair — Colour of the hair and skin — Anomalous 



