Darwin s Theory of Sexual Selection 193 



In regard to those species of fish in which both sexes are 

 equally ornamented, Darwin returns once more to his hy- 

 pothesis that the color of the male, acquired through sexual 

 selection, may be transmitted to the other sex, and then, as 

 if in doubt on this point, he adds, that it may be the result 

 of the " nature of the tissues and of the surrounding condi- 

 tions." He even makes the suggestion, somewhat further 

 on, that the colors may be warning, although it is confess- 

 edly unknown that these fish are distasteful to fish-devouring 

 animals. 



In amphibians the crest on the back of the male triton, 

 which becomes colored along its edge, is described as a second- 

 ary sexual character. The vocal sacs, present in some species 

 of frogs, are found sometimes in both sexes, but more highly 

 developed in the males. In other species, as in the toad, it 

 is the male alone that sings. In the reptiles we find that the 

 two sexes of the turtles are colored alike, and this holds also 

 for the crocodiles. Some male turtles make sounds at the 

 breeding season, and the same is true for the crocodiles, the 

 males of which are said to make a " prodigous display." In 

 snakes the males are smaller, as a rule, than the females, and 

 the colors are more strongly pronounced, and although some 

 snakes are very brilliantly colored, Darwin puts this down 

 either to protective coloration, or to mimicry of other kinds 

 of snakes. But surely the extremely brilliant colors of many 

 snakes cannot be accounted for in any of these ways. The 

 cause of the color of the venomous kinds, that are supposed 

 to be imitated by the others, " remains to be explained and 

 this may perhaps be sexual selection." 



" It does not, however, follow because snakes have some 

 reasoning power, strong passions and mutual affection, that 

 they should likewise be endowed with sufficient taste to 

 admire brilliant colors in their partners, so as to lead to the 

 adornment of the species through sexual selection. Never- 

 theless, it is difficult to account in any other manner for the 



