62 ON TREJIATODE PARASITES. 



diverticula. The eggs do not show the same tendency to be 

 massed towards the left side as is seen in G. affmis. They are 

 of relatively enormous size, measuring •029-*034 x •015--020 mm., 

 the average being '032 x "0175 mm. There are usually about 

 30-100 eggs. 



Gymnophallus ovoplenus, sp. n. 



This fourth species, which is undoubtedly distinct from all the 

 others, was characterised by its extremely minute size and by the 

 enormous overgrowth of the uterus, which completely filled the 

 body. The numerous eggs seen in the smallest specimen entirely 

 obscured the other organs, rendering a description of the internal 

 anatomy impossible. On that account, it is to some extent 

 a matter of conjecture as to whether the species actually belongs 

 to the genus Gymnophallus or not, but from its general appearance 

 there seems little doubt that it does. 



It is a very plump, subcylindrical species with somewhat 

 pointed ends. The length is •11--13 mm. and the maximum 

 breadth about '07 mm. The oral sucker does not measure more 

 than -024 mm. in diameter, and it is not much larger than the ventral 

 sucker ('019 mm.), which is situated about two-thirds of the body- 

 length from the anterior end. The uterus fills the body, except 

 for a small space at the tip of the tail which usually remains 

 free. Anteriorly the eggs are packed tightly around the oral 

 sucker, rendering it almost invisible. They measure -OIG-'OID x 

 •011--012 mm. 



It was at first thought that these specimens were simply young 

 forms of either G. affinis or G. cedemice, but it seems impossible 

 that such can be the case. Even when the animal is only -12 mm. 

 long the uterus attains a stage of hypertrophied development 

 which is never seen in either of the other species even when 

 twice as large. It might be conjectured that either or both of 

 these species may become prematurely ripe and that egg-pro- 

 duction falls off later. This, however, is a hypothesis which has 

 nothing to support it. Moreover, as has already been mentioned, 

 specimens measuring -13 mm. and closely resembling G. affinis 

 have been found, and in them the u.terus occupied only a relatively 

 small proportion of the body. 



Judging by the relative sizes of the suckers, this species is 

 more closely allied to G. cedemice than to G. affinis. 



References. 



(1) Herdman, W. a. 1903-6. — Report on the Pearl Fisheries of 



the Gulf of Manaar. 



(2) Jameson, H. L. 1902.—" On the Origin of Pearls." P.Z.S. 



1902, pp. 140-166. 



(3) Lebour, M. Y. 1906.— a Preliminary Report on a Trematode 



Parasite in Cardium edule. Northumberland Sea Fisheries 

 Report for 1905 (1906). 



