302 TEE DESCENT OF MAN. 



water prawns (Palaernon) the right leg is actually longer than 

 the whole body.* The great size of the one leg with its 

 chelae may aid the male in fighting with his rivals; but this 



Fig. 5. Anterior part of body of Callianassa 'from Milne-Edwards), 

 showing the unequal and different!' -constructed rig r and 

 left hand chelae of the male. 



N. B. The artist by mistake has reversed the drawing, and made the 

 left-hand chela the largest. 



Jig. 6. Fig. 7. 



Fie. 6. Second leg of male Orchestia Tucuratinga (from Fritz Muller). 

 Fig . 7. Ditto of female. 



will not account for their inequality in the female on the 

 opposite sides of the body. In Geiasimus, according to a 



*See a paper by Mr. C. Spence Bate, with figures in " Proc. 

 Zoolog. Soc./' 1868, p. 363; and on the nomenclature of the genus, 

 ibid. p. 585. I am greatly indebted to Mr. Spence Bate for nearl v all 

 the above statements with respect to the chelae of the higher 

 crustaceans. 



