90 THE FRESH- WATER CRAYFISH— THE CAPE CRAWFISH 



being very large. [In Jasus this claw is absent, but in the female 

 the posterior walking leg of each side bears a small claw or chela.] 

 (iv) The large fan-shaped appendages or uropods of the 6th ab- 

 dominal segment which, together with the telson, form the tail. 



Fig. 28.— The European Fresh-water Crayfish (Astacua). 



2. Examine the specimen from the ventral surface and note : 



(a) The opening of the " green gland " or nephridium at the base of each 



antenna. 



(b) The appendages of the head and the first three pairs of thoracic append- 



ages crowded together. 



