348 WILLIAM NrCOLL. 



developed, usually in one layer, sometimes in two or three. 

 The bifurcation takes place a short distance in front of the 

 ventral sucker, almost on the same level as the genital aper- 

 ture. The diverticula pass round on either side of the 

 sucker ; behind it they are directed in towards the middle 

 line of the body, pursuing a more or less zigzag course. 

 Further back they again bend out to pass round the outer 

 border of the testes, and their terminal part, which is usually 

 somewhat dilated, again approximates the middle line. Like 

 the oesophagus the diverticula are wider dorso-ventrally than 

 from side to side. The characteristic features of the alimen- 

 tary system are thus its shape, the slightly sacculated condi- 

 tion of its walls, and the latteral flattening. 



The excretory system is one of the most peculiar features 

 of this Trematode, and differs very much from the types 

 usually found. The vesical proper (Plate 21, fig. 1, Ed\) is not 

 of large size, but is remarkable for its shape. The outline is 

 very irregular, there being on each side about four short 

 unsymmetrical branches, which may be bifurcated at their 

 ends. It is situated at the posterior end of the body; the 

 aperture is not terminal, but is a little forward on the dorsal 

 surface. The excretory system comprises, in addition, two 

 median and two lateral trunks, which communicate pos- 

 teriorly with the vesicle. The median trunks are wide, 

 compressed dorso-ventrally, and occupy a dorsal position. 

 The lateral trunks are more irregular, and fill up the side- 

 areas of the body. Their lumen is traversed by numerous 

 septa, which divide it, as it were, into a system of anasto- 

 mosing vessels. Viewed from externally the appearance 

 produced is that of a mosaic of irregular patches, amongst 

 which the excretoi'y fluid circulates. The lumen of the 

 median trunks is not so much divided. Behind the ventral 

 sucker they begin to branch, and communications between 

 the two trunks of one side, as well as between the two median 

 trunks, are not infrequent. At the level of the ventral 

 sucker the median trunks each send out a branch, which 

 forms anastomosing connections almost completely surround- 



