304 THE 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. Orcbestia Darwiryi (from Fritz Muller\ showing the differently- 

 constructed chelze of the two male forms. 



habits of life, anil 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 puber) was seen by a sou of Mr. Bate fighting with 

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

 and had every limb tcra from its body. When several 



