FISHES. 375 



CHAPTER XII. 



SECONDAKY SEXUAL CHARACTEKS OF FISHES, 

 AMPHIBIANS 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 the breeding-season alone Fishes with both 

 sexes brilliantly colored Protective colors The less conspicu- 

 ous 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: Differences in structure and 

 color between the sexes Vocal organs. REPTILES : Chelonians 

 Crocodiles Snakes, colors in some cases protective 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 lowest class, that 

 of fishes. The males of Plagiostomous fishes (sharks, rays) 

 and of Chimaeroid 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 temporarily 

 developed during the breeding-season ; and Dr. Giinther 

 suspects that they are brought into action as prehensile 

 organs by the doubling inward and downward of the two 

 sides of the body. It is a remarkable fact that the females 

 and not the males of some species, as of Raia clavata, have 

 their backs studded with large hook-formed spines.* 



The males alone of the capelin (Mallotus villosus, one of 



* Yarrell's "Hist, of British Fishes," vol. ii, 1836, pp. 417, 425, 

 436. Dr. Giinther informs me that the spines in R clavata are 

 peculiar to the female. 



