446 LARVAL TREMATODES OF THE NORTHUMBERLAND COAST. 



reach to about the level of the centre of the ventral sucker, 

 which measures o"oi9 mm. across. Two faint excretory canals 

 run from near the anterior sucker and unite posteriorly in a 

 pore. Some reproductive organs are present in the shape 

 (first) of a penis sac (?) which appears to run in front of and 

 open at the side of the ventral sucker, (secondly) of two round 

 masses at the posterior end, presumably the vitellaria, and 

 (thirdly) of a less conspicuous similarly shaped body slightly 

 in front of these. 



This Trematode is very common in the Palvdestrina 

 stagnalis from Fenham Flats, and occurs in 50 per cent, of 

 these. It also occurs at Stranraer in about 2 per cent. I 

 cannot find anything recorded about this and the following 

 species, and think they have not been found before. 



Cercaria pirum (see Plate IX. F, G). In the liver oi Pahi- 

 destrina stagnalis another cercaria was found. It occurred 

 encysted in 4 per cent, of the Fenham Flats specimens from 

 October to December, 1906. From the way the cercariae 

 were packed in the liver I should think that they had encysted 

 in sporocysts very much in the same way as C. oocysta, and 

 that the walls of the sporocysts had dissolved, but no traces 

 of these could be seen. The cysts and enclosed cercariae are 

 colourless and transparent, the cysts being spherical and 

 measuring o"o8 mm. in diameter. The cercaria when pressed 

 out carefully from the cyst is seen to be pear-shaped with a 

 very broad flat base, and measures 0*20 mm. in length, the 

 body being covered with small sharp spines, which are more 

 conspicuous near the head, giving it a rough appearance. 

 The anterior sucker is 0*026 mm. across, and the ventral 

 sucker is about the same size, and occurs about three-parts of 

 the way down the body. The oral sucker leads directly into 

 a broad-lipped pharynx, from which a narrow and straight 

 intestine runs to about the centre of the body, where it 

 bifurcates into two short lobes, the ends of which are nearly 

 on the same level as the posterior border of the ventral sucker. 

 Two excretory canals run down from the sides of the oral 



