224 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



of the abdomen the first two pairs of abdominal appendages (Fig. 102, B, 

 Oj and a^ are, as already mentioned, modified in the male for sexual 

 purposes, while in the female they are so reduced in size as to have 

 almost disappeared. 



In the region in front of the abdomen the appendages are stout 7-jointed 



Fig. 102. 



Dorsal (A) and ventral (B) views of a male Crayfish. A^, First antenna (antennule) ; A2, second 

 antenna ; ai-a, abdominal appendages ; An, anus ; E, eye ; Li.j, walking legs ; mp.^, third 

 maxilliped ; t, telson. 



walking legs — five pairs. In the young Norway Lobster, which is a 

 free-swimming larva, these appendages show the same three component 

 parts as the abdominal appendage, but as development goes on the 

 exopodite disappears, the walking leg of the adult consisting entirely of 



