330 



SEXUAL SELECTION. 



Part II. 



In the higher crustaceans the anterior legs form a 

 pair of chelae or pincers, and these are generally 

 larger in the male than in the female. In many species 

 the chelae on the opposite sides of the body are of 

 unequal size, tbe right-hand one being, as I am in- 



Fig. 4. Anterior part of body of Callianassa (from Milne-Edwards), showing the unequal 

 and differently -constructed right and left-hand chela? of the male. 



N.B.— The artist by mistake has reversed the drawing, and made the left-hand chela 

 the largest. 



Fig. 5. 



Fig. 6. 



Fig. 5. Second leg of male Orchestia Tucuratinga (from Fritz Miiller). 

 Fig. 6. Ditto of female. 



formed by Mr. C. Spence Bate, generally, though not 

 invariably, the largest. This inequality is often much 

 greater in the male than in the female. The two chelae 

 also often differ in structure (figs. 4 and 5, 6), the smaller 

 one resembling that of the female. What advantage 



