MAMMALS-SUMMARY. 549 



When the male differs in color from the female, he generally 

 exhibits darker and more strongly-contrasted tints. We do not 

 in this class meet with the splendid red, blue, yellow, and green 

 tints, so comrrion with male birds and many other animals. The 

 naked parts, however, of certain Quadrumana must be excepted; 

 for such parts, .often oddly situated, are brilliantly colored in 

 some species. The colors of the male in other cases may be 

 due to simple variation, without the aid of selection. But when 

 the colors are diversified and strongly pronounced, when they 

 are not developed until near maturity, and when they are lost 

 after emasculation, we can hardly avoid the conclusion that they 

 have been acquired through sexual selection, for the sake of orna- 

 ment, and have been transmitted exclusively, or almost exclusive- 

 ly, to the same sex. When both sexes are colored in the same 

 manner, and the colors are conspicuous or curiously arranged, 

 without being of the least apparent use as a protection, and espe- 

 cially when they are associated with various other ornamental 

 appendages, we are led by analogy to the same conclusion, name- 

 ly, that they have been acquired through sexual selection, al- 

 though transmitted to both sexes. That conspicuous and diversi- 

 fied colors, whether confined to the males or common to both 

 sexes, are as a general rule associated in the same groups and 

 sub-groups with other secondary sexual characters serving for 

 war or for ornament, will be found to hold good, if we look back 

 to the various cases given in this and the last chapter. 



The law of the equal transmission of characters to both sexes, 

 as far as color and other ornaments are concerned, has prevailed 

 far more extensively with mammals than with birds; but weap- 

 ons, such as horns and tusks, have often been transmitted either 

 exclusively or much more perfectly to the males than to the fe- 

 males. This is surprising, for, as the males generally use their 

 weapons for defense against enemies of all kinds, their weapons 

 would have been of service to the females. As far as we can see, 

 their absence in this sex can be accounted for only by the form 

 of inheritance which has prevailed. Finally, with quadrupeds the 

 contest between the individuals of the same sex, whether peace- 

 ful or bloody, has, with the rarest exceptions, been confined to 

 the males; so that the latter have been modified through sexual 

 selection, far more commonly than the females, either for fight- 

 ing with each other or for alluring the opposite sex. 



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