134 



CRUSTACEA — PERACARIDA 



absent. Very large lamellae grow out from the bases of the 

 thoracic limbs to form a brood-pouch, and in this manner the 

 adult condition is attained. 



The final complication in the life-histories of these Isopoda 

 is reached by the family Entoniscidae, which are parasitic when 



Fig. 92. — Bo2)yrus fougerouxi. A, 

 Ventral view of female carrying a 

 male {M) between her abdominal 

 appendages, x 8 ; B, ventral 

 view of part of head of female, 

 the maxillipedes and the left 

 mandible having been removed. 

 A.l, A. 2, 1st and 2nd antennae ; 

 M, male ; Mn, right mandible ; 

 3Ix, left maxillipede ; 0, ocste- 

 gite ; T, left 4th thoracic append- 

 age or 3rd leg. (After Bonnier.) 



adult inside the thoracic cavity of Brachyura and Paguridae, 

 The cephalothorax of a Carcinus maenas, which contains an adult 

 Portunion maenadis (F), is shown in Fig. 93. The parasite is 

 of a reddish colour when alive. 



The Entoniscidae pass through a free living Epicaridian 

 and Cryptoniscus stage, and become adult males in the Bopyrus 

 stage. It is stated, however, by Giard and Bonnier ^ that these 

 individuals, which actually function as males, never grow up 



1 Tmv. Inst. Lille, v., 1887. 



