SEXUAL SELECTIOIS'. 



CHAPTER XII. 



Secondaby Sexual Ciiaracteus of Fishes, Amphibi- 

 ans, AND Reptiles. 



Fishes : Courtship and Battles of the Males. — Larger Size of the Females. — 

 Males, Bright Colors and Ornamental Appendages ; other Strange 

 Characters. — Colors and Appendages acquired by the Males during tho 

 Breeding-season alone. — Fishes with both Sexes brilliantly colored. — 

 Protective Colors. — The less Conspicuous Colors of the Female cannot 

 be accounted for on the Principle of Protection. — Male Fishes building 

 Nests, and takingChargeof tlie Ovaand Young. Amphibians: Ditfer- 

 ences in Structure and Color between the Sexes. — Vocal Organs. Rep- 

 tiles : Chelonians. — Crocodiles. — Snakes, Colors in some Cases pro- 

 tective. — Lizards, Battles of. — Ornamental Appendages. — Strange Dif- 

 ferences in Structure between the Sexes. — Colors. — Sexual Ditfcrences 

 almost as great as with Birds. 



"We have now arrived at the great svth-kingdom of the 

 Yertebrata, and will eonimence with the lowest class, 

 nanuly, Fishes. The males of Plagiostomous fishes 

 (sharks, rays) and of Ciiimreroid fishes are provided with 

 claspers which serve to retain the female, like the various 

 stnu'tures possessed by so many of the lower animals. 

 Besides the claspers, the males of many rays have clus- 

 ters of strong sharp spines on their heads, and several 

 rows along "the upper outer surface of their pectoral 

 iius." These are present in the males of some species, 



wiruli have the other parts of their bodies smooth. They 

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