CONTENTS 15 



CHAPTER XV 



BIRDS — continued 



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

 others, are brightly colored — On sexually limited inheritance, as ap- 

 plied to various structures and to brightly colored plumage — Nidiflca- 

 tion in relation to color — Loss of nuptial plumage during the winter 678 



CHAPTER XVI 



BIRDS — coticluded 



The immature plumage in relation to the character of the plumage in both 

 sexes when adult — Six classes of cases — Sexual differences between 

 the males of closely allied or representative species — The female as- 

 suming 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 coloring — Conspicu- 

 ously colored birds — Novelty appreciated — Summary of the four chap- 

 ters on birds 598 



CHAPTER XVII 



SBOONDAKT SEXUAL CHAEACTBES 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 shown by either sex in the pairing of quadrupeds 646 



CHAPTER XVIII 



SEOONDAET SEXUAL OHAEACTERS OP MAMMALS — Continued 



Voice — Remarkable sexual peculiarities in seals — Odor — Development of 

 the hair — Color of the hair and skin — Anomalous case of the female 

 being more ornamented than the male — Color and ornaments due to 

 sexual selection — Color acquired for the sake of protection — Color, 

 though common to both sexes, often due to sexual selection — On the 

 disappearance of spots and stripes in adult quadrupeds — On the colors 

 and ornaments of the Quadrumana — Summary . , . . &9 



