THE DESCENT OF MAN 



AND 



SELECTION IN RELATION TO SEX 



CHAPTER XII 



3ECONDAEY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, 

 AND REPTILES 



£^SH£S: 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 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 seies — Yocal organs. Rep- 

 tiles: Chelonians — Crocodiles — Snakes, colors in some eases protec- 

 tive — Lizards, battles of^— Ornamental appendages — Strange differences 

 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 low- 

 est class, that of Fishes. The males of Plagi- 

 ostomous fishes (sharks, rays) and of Chimseroid fishes are 

 provided with claspers which serve to retain the female, 

 like the various structures possessed by many of the lower 

 animals. Besides the claspers, the males of many rays have 

 clusters 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 

 other parts of their bodies smooth. They are only tempo- 

 rarily developed daring the breeding season ; and Dr. Gun- 

 ther suspects that they are brought into action as prehensile 

 organs by the doubling inward and downward of the two 



(431) 



