TREMATODES OF THE NORTHUMBERLAND COAST 43 



colour with a patch of bright greenish brown (the eggs) at the 

 posterior part of the body. The cuticle is unarmed. When 

 dead and pressed under a cover slip the worm measures 

 i-8o-2-3o mm. in length, but may be much longer than this 

 when ahve. The maximum breadth, about i ■16-1-33 mm., is 

 in the region of the ventral sucker. The shape is a broad 

 oval with the ends more rounded than in S.furciger. The 

 ventral sucker is almost exactly in the centre, and behind this 

 the hind end of the body is taken up by the eggs, the uterus 

 winding in many twists and masking most of the other organs. 

 Like S. furciger the body has a round section in the anterior 

 part, but flattens in the region of the ventral sucker. Both 

 suckers are circular, the oral measuring o'32-o'4o mm. across 

 and the ventral o'6o-o-8o mm., their relative sizes being about 

 1 :2. The oral sucker opens externally in a large mouth that 

 leads to a very short prepharynx, and this to a muscular 

 pharynx. There is a short and narrow oesophagus, branching 

 very soon into the thin intestinal lobes reaching, as in S. 

 furciger, to beyond the testes for about the same length as 

 these organs. The excretory bladder is not so conspicuous 

 as in -S*. furciger, because in all the specimens it is clear 

 instead of full of dark matter. It is forked in much the same 

 way as in S. furciger, the single stem lying dorsally and the 

 lobes (which are swollen in front) coming forward ventrally ; 

 the latter reach to beyond the posterior level of the oral sucker 

 when the worm is at rest. The hinder part of the excretory 

 and digestive system is usually completely hidden, in pressed 

 examples, by the eggs and vitellaria. The genital pore occurs 

 close to the pharynx, to the left side above the fork of the 

 intestine, the male and female ducts opening into a genital 

 sinus, the male on the right and the female on the left. The 

 form of the sinus and the openings closely resemble those of 

 S. furciger. The testes are oval bodies, lying dorsal to and 

 just behind the ventral sucker, and ventral to the intestinal 

 lobes. They are oval and measure o'i2 mm. in length. The 

 vasa deferentia are very thin, and run forwards from the testes 

 to the vesicula seminalis, which is divided into two almost 



