SEXUAL SELECTION". 



CHAPTER XII. 



Secondary Sexual Characters oe Fishes, Amphibi- 

 ans, and -Reptiles. 



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

 Males, Bright Colors and Ornamental Appendages; other Strange 

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

 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 taking Charge of the Ova and Young. Amphibians : Differ- 

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

 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 Differences 

 almost as great as with Birds. 



We have now arrived at the great sub-kingdom of the 

 Vertebrata, and will commence with the lowest class, 

 namely, Fishes. The males of Plagiostomous fishes 

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

 claspers which serve to retain the female, like the various 

 structures 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 

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



which have the other parts of their bodies smooth. They 



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