Chap. XXI. AND CONCLUDING REMARKS. 397 



with mammals, birds, reptiles, fishes, insects, and even 

 crustaceans, the differences between the sexes follow 

 almost exactly the same rules. The males are almost 

 always the wooers ; and they alone are armed with spe- 

 cial weapons for fighting with their rivals. They are 

 generally stronger and larger than the females, and are 

 endowed with the requisite qualities of courage and pug- 

 nacity. They are provided, either exclusively or in a 

 much higher degree than the females, with organs for 

 producing vocal or instrumental music, and with odori- 

 ferous glands. They are ornamented with infinitely 

 diversified appendages, and with the most brilliant or 

 conspicuous colours, often arranged in elegant patterns, 

 whilst the females are left 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 securing or charming the female 

 are often developed in the male during only part of the 

 year, nauaely the breeding season. They have in many 

 cases been transferred in a greater or less degree to 

 the females ; and in the latter case they appear in 

 her as mere rudiments. They are lost by the males 

 after emasculation. Generally they are not developed 

 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 female resembles her young offspring through- 

 out lite. In almost every great class a few anomalous 

 cases occur in which there has been an almost complete 

 transposition 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 differences between the sexes in so many 



