On Dissotrema papillatum. q 



The correctness of the contention of Looss, that the "phar- 

 ynx" of authors in the Paramphistomatidœ is in reality the oral 

 sucker is especially evident in this genus. 



Next the pharynx comes the oesophagus, a very short section 

 of the alimentary canal lined by the direct continuation of the 

 cuticle of the former, which terminates abruptly behind and gives 

 place to the epithelium of the intestine. Into the oesophagus 

 open a number of unicellular glands, the œsophageal or salivary, 

 the cells of which lie at some distance from the lumen, with which 

 they are connected by long ducts. As a general rule these salivary 

 glands stain lighter than the prepharyngeal. 



The intestinal caeca are short and diverge at an angle of about 

 40° and are broader anteriorly and narrower posteriorly. In four 

 specimens mounted in toto a caecum measured respectively 616 x 

 264//, 616x300/^, 598x300/« and 510x229//, as seen dorsoventral- 

 ly. The hind ends of the caeca lie slightly behind the middle of the 

 whole length of the body. The caeca are surrounded by double 

 layers of muscle fibres, an inner of circular and an outer of longi- 

 tudinal ones. The latter may be looked upon as the continuation 

 of the corresponding layer of the prepharynx, because several of 

 its fibres are seen to be directly continued into those of the other 

 along the outside of the pharynx. The intestinal epithelium, which 

 rests on a thin basement membrane, is of various thickness, but 

 usually the cells are 12-32// in height, and their free ends show the 

 pseudopodia-like processes frequently seen in digenetic trematodes. 



The excretory pore lies at the top of the papilla already men- 

 tioned near the posterior end of the body; hence the papilla may 

 be fitly called the excretory papilla (fig. 2). The pore leads into 

 an elongated bottle-shaped cavity, the excretory vesicle, lying 

 on the dorsal side of the acetabulum and extending forwards to 

 about its middle, where it divides right and left into the two 

 main excretory vessels. These diverge towards the lateral side 

 of the body and proceed forwards with light windings just on 

 the outside of the genital organs and the gut to about the level 

 of the hind end of the brain. Here it turns upon itself and 

 forms the recurrent vessel, which proceeds backwards, closely 

 following its former course, and divides into several small branches 



