ISOPODA 



357 



ordinary isopod form, though heavily built, and with piercing mouth 

 parts and some of the legs hooked. Its broad uropods form a tail 

 fan. Bopyrus (Fig. 263), in the gill chamber of prawns, with dwarf 



Th.Q 



Fig. 262. A, Asellus aquaticus. Male viewed from above. From Leuckart 

 and Nitsche. an.' antennule; an." antenna; ab.6, the last pair of abdominal 

 limbs; t. testes with their efferent canals: the nervous system is shown in 

 black ; Th.z-Th. 8, thoracic limbs. B, Aega psora. B', Maxillule of the same. 

 All after Sars. 



males, is more degenerate but still recognizable as an isopod. Crypto- 

 niscus, a " hyperparasite " on members of the Rhizocephala and a 

 protandrous hermaphrodite, is extremely degenerate. Many of 

 these parasites produce parasitic castration (see p. 344). 



