304 THI DESCENT OF MAN. 



having fought with other males during many generations^. 

 In most of the orders, especially in the highest or the 

 Brachyura, the male is larger than the female ; the para- 

 sitic genera, however, in which the sexes follow different 



Fig. 8. Orchestia Darwiiiii (from Fi-itz Muller), showintr the differently- 

 constructed chelaj of the two male forms. 



hahits of life, and most of the Entomostraca" must be 

 excepted. The chelae of many crustaceans are weapons 

 well adapted for fighting. Thus when a devil-crab (Por- 

 tunus piiber) was seen by a son of Mr. Bate fighting with 

 a Carcinus mcenas, the latter was soon thrown on its back, 

 and had every limb torn from its body. When several 



