Mycetomorplia. 577 



General Account o f t h e A n a t o m y. 



The external appearance of the parasite on tlie host is re- 

 presented in the two excellent drawings (PI. 15 Fig. 1 and 2) which 

 were made for me b}^ Mr. Edwin Wilson of Cambridge. In the 

 first figiire the parasite is seen extending under the posterior part 

 of the thorax and the three anterior abdominal segments of the 

 host. It was a very pale yellow in colour and measured nearly 1 cm 

 in breadth and 1,8 cms in length (about two-fifths the lengtli of the 

 shrimp). In the lateral view (PI. 15 Fig. 2) the pleura and appendages 

 of the adjacent segments of the host are removed to obtain a fair 

 view of the parasite and some idea is given of the shortness of the 

 peduncle and the flattening of the body where it comes into contact 

 with the ventral surface of the host. 



The external feature which distinguishes this genus at the first 

 glance from the other Rhizocephala is the number of clubshaped lobes 

 containing diverticula of the mantle cavity which come off from the 

 entire circumference of the sacshaped body and give the animal an 

 appearance not unlike that of the mushroom gland of the male 

 cockroach. The lobes are arranged in three tiers and fiftyfive of 

 them were counted altogether. They var}^ slightly in size and while 

 anteriorly they are always simple the posterior ones have a tendency 

 to fork and become hammershaped. At their attachment to the 

 central body they possess a narrow neck. 



The central part of the body is a rather elongated oval, flattened 

 on the Upper surface \), slightly convex underneath. It appears on 

 a cursory inspection to be regulär but the correct configuration is 

 obscured by the bending over of tlie lobes and when these are 

 turned back an indentation of the left border is revealed which 

 indicates the attachment of the visceral mass. It will be convenient 

 to refer to this feature throughout as the "bay". 



Another remarkable character is the thinness of the mantle 

 due to the slight development of the muscular layers. It is so thin 

 as to be nearly transparent and botli on capture and after fixation 

 the couutless numbers of Cypris larvae which fill the mantle cavity 



1) In coDsequence of the great aayranietry of the animal I sball refer 

 simply to the upper and under surfaces the former being that part 

 which is apposed to the ventral surface of the host, and to the anterior 

 and posterior parts of the parasite corresponding to the same parts 

 of the host. 



