STUDIES ON: THE DIGENETIC TREMATODES. 469 
the uterus (about a third of its length) is filled with 
numerous sperms, and functions as a receptaculum seminis 
uterinum. ‘The ova are moderate in number and of small 
size. ‘They are narrow oval in shape, with thick, tough shell, 
and measure °0424 by °0251 mm. 
Fellodistomum agnotum n. sp., Pl. 10, fig. 15. 
Among the Distomids which were obtained from the 
gall-bladder or the adjoining part of the duodenum of 
Anarrhichas lupus, there occurred a few which resembled 
Fellodistomum fellis so closely that they were included 
along with it. On later and more careful examination, 
however, they showed features which rendered their specific 
distinction comparatively easy. My attention was first 
directed towards these specimens in the course of investigating 
the size at which Fellodistomum fellis attained maturity. 
It was rather disconcerting to find that some small specimens 
had numerous ova, while other larger specimens were quite 
immature. As events have proved, the smaller specimens 
belong to a distinct species. 
Under these circumstances it is difficult to say what the 
exact habitat of this new species is. As far as my 
recollection goes, however, these were the specimens which 
occurred in the duodenum, and the true Fellodistomum 
fellis is apparently confined to the gall-bladder. Unfor- 
tunately no further opportunity has offered of confirming 
this. The new species displays the same green-coloured 
intestinal diverticula so characteristic of Fellodistomum 
fellis, but this might easily be due to bile ingested in the 
duodenum. 
The chief diagnostic features of the new species are the 
more elongated body, smaller and less prominent ventral 
sucker, the forward position of the yolk-glands, and the 
backward prolongation of the uterus. Mt is much less 
numerous than F. fellis in the proportion of 1 to 30. 
The largest specimen had a length of 3°3 mm. and a 
