676 W. G. MacCallum, 



upward. iu the otlier, tlie ventral surface is concave. The mar^in 

 of the body on each side is somewhat thinned out and forms a 

 projecting edge. The details of the anatomy worked out froni the 

 serial sections are as foUows: 



The mouth, which lies at the anterior end, opens into an elong-- 

 ated sncker. The genital cloaca surrounded" by a sncker-like mus- 

 cular arrangement is situated on the ventral snrface a very sliort 

 distance behind the mouth sucker separated froni it by about the 

 length of the mouth sucker. 



The muscular mouth sucker opens into a sort of prepharynx of 

 similar structure which, in turn, communicates with an elongated 

 club-shaped muscular pharynx. On each side the prepharynx gives 

 oif a Short muscular tube with circular and radial muscle fibres 

 and many gland cells which extend into a blind convoluted sac 

 lying on each side beside the pharynx. These lateral sacs are lined 

 by a thin cuticle and have an inner circular layer of muscle as 

 well as the loosely arranged radial layer the fibres of which run 

 out to a thin outer membrane. The short tubes connecting them 

 with the prepharynx and thus with the mouth sucker are lined with 

 thick cuticle and have several layers of circular fibres as well as 

 the radial • fibres. This seems in this instance to be a curiously 

 elaborate development of the lateral pouches from the mouth sucker 

 and it is difflcult to understand what function they can fill at such 

 a distance for they could hardly aid much in the suctorial activity 

 of the mouth parts when separated from the mouth by the narrow 

 contractile tube described. The long, club-shaped Channel from the 

 prepharynx to the intestine which opens almost directly into the 

 intestine is lined with a thick cuticle. It is relatively thin an- 

 teriorly but strengthened posteriorly by a thick circular layer of dense 

 pink-staining bands in which one sees no nuclei and which are 

 possibly muscular in nature. Outside this there is a membrane and 

 some loose tissue containing large cells with large vesicular nuclei 

 and nucleoli. 



There may be some question as to whether this thick muscular 

 portion of the Oesophagus should be regarded as a pharynx or merely 

 as a peculiarly thick oesophageal wall. In forms in which there is 

 also a sharply diflferentiated muscular structure between the mouth 

 sucker and the intestine this question would hardly arise. Here 

 however the thick oesophageal wall corresponds at least in function 

 with the pharynx of other trematodes. 



