SEXUAL SELECTION. 



CHAPTER XII. 



Secondary Sexual Characters of Fishes, Amphibians, 



ANp Reptiles. 



.Fishes : Courtsliip and battles of the males — Larger size of the 

 females — Males, bright colom's and ornamental appendages ; 

 other strange characters — Colours and appendages acquired by 

 the males during the breeding-season alone — Fishes with both 

 sexes brilHantly coloured — Protective colours — The less con- 

 spicuous colours 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 : Differences in 

 structure and colour between the sexes — Vocal organs. Rep- 

 tiles: Chelonians — Crocodiles — Snakes, colours in some cases 

 protective — Lizards, battles of — Ornamental appendages • — 

 Strange differences in structure between the sexes — Colours 

 — Sexual differences almost as great as with birds. 



o' 



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

 Yertebrata, 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 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 the other parts of their bodies 



VOL, II. B 



