196 Heredity. 



This series of forms seems to show that all twelve spe- 

 cies arc descended from a form with plain males and 

 plain females ; that this character has been retained in 

 both sexes by one species, but that the males have been 

 greatly modified in the other eleven, while in two of 

 them the females have inherited, to an imperfect degree, 

 tho modification of the males of their own species, and 

 in the other nine the females have remained stationary 

 and have shown no tendency to inherit the modification 

 of their male parents. 



In an allied genus, Enbagis, the males of most of the 

 species are decorated with beautiful metallic tints, in a. 

 diversified manner, and differ much from the females. 

 The females throughout the genus, on the other hand, 

 retain a uniform style of coloring, so that they common- 

 ly resemble each other much more closely than they re- 

 semble their own proper males. 



Darwin concludes (Variation, Vol. I., p. 378) that 

 " when the sexes of butterflies differ, the male, as a gen- 

 eral rule, is the most beautiful, and departs most from 

 the usual type of coloring of the group to which the spe- 

 cies belongs. Hence in most groups the females of the 

 several species resemble each other much more closely 

 than do the males," . . . " and this indicates that 

 the males have undergone a greater amount of modifica- 

 tion than the females" There are many striking excep- 

 tions to this law, which is general but not universal. 

 Certain of the most remarkable exceptions, such as the 

 occurrence of polymorphic female butterflies, and of the 

 various female forms among the social insects, will be 

 discussed at the end of the next chapter. 



FISHES. Darwin gives many instances of difference 

 between the sexes in fishes, and his list might be very 

 greatly increased, but one or two examples will be suf- 



