CHAPTER IX 



LOVE-MAKING AMONG FISHES 



Germinal Variations — Fishes and mate-hunting — Some remarkable 

 Sexual differences displayed by the Teeth of Rays — The 

 Double-eyed Fish — The Coloration of the Dragonet — Some 

 curious facts about Salmon — The strange use of the kidneys in 

 the Stickle-back — The Stickle-back and parental duties-^ 

 Siamese Fightmg-fish. 



Mammals, Birds, Reptiles and Amphibia, as has already 

 been shown, all exhibit practically the same line of 

 conduct in regard to their mate-hunting instincts ; all use 

 like modes of expression. And this is a very significant 

 fact. It becomes more so when we turn to the fishes, 

 for here again we meet with the same behaviour, and 

 here again we meet with the same rules in " secondary 

 sexual characters." 



An instance or two of the latter distinction between 

 the sexes should suffice. As a rule, among fishes, the 

 males are smaller than the females : commonly there 

 is no other external distinguishing feature between them. 

 In many cases, however, the males are more or less 

 strikingly different, thereby showing a departure in the 

 nature of a higher degree of complexity, or " special- 

 ization," just as obtains among the birds. And the same 



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