IV CONTENTS. 



Birds. — Variations sometimes abrupt. — Laws of Variation. — Formation 

 of Ocelli.— Gradations of Character. — Case of Peacock, Argus Pheas- 

 ant, and Urosticte . . . . . • . p. 95 



CHAPTEE XV. 



birds — continued. 



Discussion why the Males alone of some Species, and both Sexes of. other 

 Species, are brightly colored. — On Sexually-limited Inheritance, as ap- 

 plied to Various Structures and to Brightly-colored Plumage. — If idifi- 

 cation in Eelation to Color. — Loss of Nuptial Plumage' during the 

 "Whiter ........ 147 



CHAPTEE XVI. 



birds — concluded. 



The Immature Plumage in Eelation to the Character of the Plumage in 

 both Sexes when Adult. — Six Classes of Cases. — Sexual Differences 

 between the Males of Closely-allied or Eepresentative Species. — The 

 Female assuming the Characters of the Male. — Plumage of the Young 

 in Eelation to the Summer and "Winter Plumage of the Adults. — On 

 the Increase of Beauty in the Birds of the "World. — Protective Color- 

 ing. — Conspicuously-colored Birds. — Novelty appreciated. — Summary 

 of the Four Chapters on Birds ..... 175 



CHAPTEE XVII. 



SECONDARY SEXUAL CHARACTERS OP 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 "Weap- 

 ons.— Their High Importance.— Greater Size of the Male. — Means of 

 Defence. — On the Preference shown by either Sex in the Pairing of 

 Quadrupeds ....... 228 



■ 



CHAPTEE XVIII. 



SECONDARY SEXUAL CHARACTERS OF MAMMALS Continued. 



Voice. — Bemarkable 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.— 



