734 ON SOME TREMATODK PARASITES, 



ably, and in preserved specimens the shape in transverse sections 

 in almost invariably somewhat flattened oval. They are widest 

 just behmd the ventral sucker, rounded in front, but gradually 

 tapering to a long point behind ; there is a slight constriction near 

 the ventral sucker, just in front of the widest part of the body. 

 The average size is 11-2 mm., long, by 2-34 mm. wide. 



The cuticle is thick and tough, beset with numerous sharp- 

 pointed spines, closely set in the anterior region of the body, but 

 gradually becoming sjoarse and scattered towards the posterior 

 extremity. In the body-wall, the longitudinal muscles are arranged 

 in columns separated from one another by connective tissue cells 

 (Fig. 9). 



The suckers are very large; the oral spherical, with its aperture 

 ventrally placed near the anterior end ; the ventral, placed close to 

 the oral, is also spherical, nearly as wide as the body, and deeply 

 implanted in it. The average diameters are, oral 0-6G mm., ventral 

 1-32 mm.; ratio of oral to ventral, 1:2. The relative size is very 

 constant, being practically the same in every specimen measured. 



The pharynx, much smaller than the oral sucker, joins it through 

 a prajpharynx of length rather less than its own. There is practi- 

 cally no oesophagus, and the intestinal limbs run out to the sides 

 of the body, and then proceed, in a pretty straight course, to end a 

 little distance in front of the i^osterior extremity. They are quite 

 simple in form, showing no signs of lateral caeca. 



The excretory system of vessels is very richly developed, and 

 exhibits some very marked peculiarities. The main stem of the 

 vesicle, which opens by a small pore at the extreme posterior end, 

 is a long wide tube reaching up to the level of the posterior testis, 

 where it divides into four longitudinal branches that run forwards 

 to the anterior end of the body. Both from the main stem and its 

 foi;r branches, a series of short lateral branches proceed 

 towards the surface, and break up into a number of branches 

 that lie in the parenchyma among the yolk-cells, many 

 of tliem reacliing the inner aspect of the cuticle. In this 

 respect, as in others to be pointed out below, they resemble 

 the condilion found in Mesnulus grandis R.,(Braun, 5). The four 



