SEXUAL SELECTION 



355 



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 parasitic 

 genera, however, in which the sexes follow different habits 



Bto. 8.— Orohestia Darwinii (from Fritz Muller), showing the differently coastruoted 

 chelae of the two male forms. 



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 {Portunus puber) 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 



