204 Heredity. 



amount of difference between the sexes is also incom ^ra- 

 lly less than that which frequently occurs in the last 

 class ; so that the cause of the difference, whatever ii may 

 have been, has acted upon the females in the present class 

 either less energetically or less persistently than on the 

 males in the last class. (Descent of Man, II. p. 198.) 



MAMMALS. Among the mammalia the sexes often 

 differ in their weapons of offence and defence, as we see 

 in the deer, when the horns are usually absent in the 

 female ; in their voices, as in the case with the cow and 

 bull; in odor, as goats for example, and in the musk 

 deer, where both the musk-producing organ and other 

 organs of a similar character are confined to the male; 

 in color, as in many antelopes, and in the character and 

 distribution of the hair, as we may see by comparing the 

 lion with the lioness, or the human male with the hu- 

 man female. 



A little thought will show that among the mammals, 

 as in other groups of the animal kingdom, the males are 

 more modified than the females. 



Thus man differs from woman by the possession of a 

 beard, but the boy resembles the girl or the mature fe- 

 male, thus showing that the human race is influenced 

 by the general law of which we have seen the evi- 

 dence in so many groups of animals, and that the adult 

 female is more like the young of both sexes than the 

 adult male. So, too, the young stag, or the young male 

 goat, resembles the adult female in the absence of horns. 



The fact that different human races are characterized 

 by the presence or absence of a beard in the males, and 

 that the horns of different species of deer differ very 

 greatly, shows that the males of allied species of mam- 

 mals differ more than the females. 



Among the mammalia we sometimes find that the 



