442 TREMATODES OF THE NORTHUMBERLAND COAST 



but, roughly speaking, there appeared to be about 56 in each 

 row. Each spine in the anterior row is placed exactly in 

 front of the corresponding spine in the posterior row, and does 

 not alternate with it. 



The oral sucker leads to a short prepharynx cio mm. long, 

 and a muscular pharynx slightly longer than it is broad. 

 From this runs a long narrow oesophagus o'3o mm. long, 

 branching a short way in front of the ventral sucker into two 

 narrow lobes reaching the posterior end about o"6o mm. from 

 its termination. 



The excretory vesicle is a long narrow sac running forward 

 and reaching beyond the posterior testis. It gives off lateral 

 branches which divide continually in the anterior part of the 

 body in a sort of network of ducts running out horizontally 

 from the laterals, which terminate in a single curved tube on 

 each side of the oral sucker. 



The genital pore occurs in the median plane just anterior 

 to the ventral sucker and below the fork of the intestine, the 

 male and female ducts opening side by side, the male on the 

 right and the female on the left. 



The testes are two oval bodies situated one in front of the 

 other in the posterior part of the body about 2*4 mm. from 

 the end. They are closely apposed, the front testis being 

 slightly larger than the other, the measurements of their long 

 axes, which lie longitudinally, being 0*24 mm. and o'2o mm. 

 respectively. The vasa deferentia run up to a long narrow 

 cirrus sac which extends about o*6o mm. beyond the ventral 

 sucker. 



The cirrus sac makes one or two bends, so that it has 

 rather a twisted appearance. The portion behind the ventral 

 sucker is occupied by the vesicula seminalis, and anterior to 

 this is a long cirrus. No pars prostatica was observed. The 

 cirrus sac runs dorsal to the ventral sucker, and opens 

 ventrally by the side of the vagina. The cirrus is extremely 

 long, and is usually exserted for about half its length. It has 

 the form of a long narrow tube with a thick wall, the inside of 



