790 THE DESCENT OF MAN 



allow of the feelings of love and jealousy, or of the exer- 

 tion of choice. When, however, we come to the Arthro- 

 poda and Yertebrata, even to the lowest classes in these two 

 great Sub-Kingdoms, sexual selection has effected much. 



In the several great classes of the animal kingdom — in 

 mammals, birds, reptiles, fishes, insects, and even crusta- 

 ceans — the differences between the sexes follow nearly the 

 same rules. The males are almost always the wooers; and 

 they alone are armed with special weapons for fighting 

 with their rivals. They are generally stronger and larger 

 than the females, and are endowed with the requisite qual- 

 ities of courage and pugnacity. They are provided, either 

 \exclusively or in a much higher degree than the females, 

 with organs for vocal or instrumental music, and with odor- 

 iferous glands. They are ornamented with infinitely diver- 

 sified appendages, and with the most brilliant or conspicuous 

 colors, often arranged in elegant patterns, while the females 

 are unadorned. When the sexes differ in more important 

 structures, it is the male which is provided with special 

 sense organs for discovering the female, with locomotive 

 organs for reaching her, and often with prehensile organs 

 for holding her. These various structures for charming or 

 secaring the female are often developed in the male during 

 only part of the year, namely, the breeding season. They 

 have in many cases been more or less transferred to the 

 females; and in the latter case they often appear in her 

 as mere rudiments. They are lost or never gained by the 

 males after emasculation. Generally they are not devel- 

 oped in the male during early youth, but appear a short 

 time before the age for reproduction. Hence in most cases 

 the young of both sexes resemble each other; and the fe- 

 male somewhat resembles her young offspring throughout 

 life. In almost every great class a few anomalous cases 

 occur, where there has been an almost complete transposi- 

 tion of the characters proper to the two sexes; the females 

 assuming characters which properly belong to the males. 

 This surprising uniformity in the laws regulating the dif- 



