290 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



but is generally very nearly twice the size of the oral 

 sucker. It is situated rather behind the middle of the 

 body, and in the dead worm, usually on an elevated part 

 of the latter. The openings of both suckers are very 

 nearly circular in outline. 



The pharynx is small and oval in shape. There is 

 no distinct oesophagus and no real undivided section of 

 the intestine. From the pharynx the intestinal rami 

 pass transversely to the margins of the body, and then 

 run back as wide voluminous vessels to near the posterior 

 extremity. In the worms, after killing in fresh water, 

 and subsequent preservation in formalin, the walls of the 

 intestine, when seen in optical section, have crenulated 

 outlines. 



In the living worms the excretory system is very 

 obvious, but disappears entirely after preservation, and 

 is only indistinctly seen on staining with carmine. The 

 main vessel runs transversely across the body just behind 

 the pharynx, then backwards as two very prominent, 

 rather wide vessels forming a loop. These unite at 

 about the mid transverse line of the ventral sucker, and 

 then pass back in the median line of the body to the 

 posterior extremity. The excretory pore is situated 

 terminally. Often at the summit of a small papilla. 



The vitellaria lie far back, about halfway between 

 the posterior margin of the ventral sucker and the 

 posterior extremity of the body. They are rather large 

 bodies, quite regular in outline, spherical, or slightly 

 flattened dorso-ventrally, sometimes oval and elongated 

 in the longitudinal axis of the body. They are made 

 up of a great number of small glandules, but the whole 

 structure is enclosed in a distinct capsule, a short trans- 

 verse duct unites them and from this the vitelline duct 

 passes forwards to the ovary. The latter is a rounded 



