LARVAL TREMATODES OF THE NORTHUMBERLAND COAST. 437 



Larval Trcmatodes of the Northuiiiherlaud Coast. By 

 Marie V. Lebou6', B.Sc. (Armstrong College, New- 

 castle-upon-Tyne). 



(Plates IX.-XIII.)SiuruM/^ H'^^ 



Trematodes have been much neglected in this country, 

 especially the younger stages. This is a curious fact, since 

 one has only to examine a few of the commonest Mollusca 

 from some favourable locality to find these larval Trematodes 

 in abundance. So far as I know no digenetic Trematodes 

 have been recorded for the Northumberland coast with the 

 exception of a few larval forms recently described by myself*. 



It is, however, not only in Northumberland that Trematodes 

 are little known, but all over Great Britain, and one could 

 almost count on one's fingers the larval Trematodes hitherto 

 noticed in this country. It seems therefore that there is a real 

 need for workers in this field, and whilst investigating the 

 Northumberland mussel beds I have tried to find out as much 

 as possible about the larval Trematodes, my work giving 

 me exceptional opportunities for the purpose, especially on 

 Fenham Flats near Holy Island. The younger stages, i.e., 

 sporocysts and rediae, with enclosed cercariae, occur in 

 Mollusca exclusively. Independent encysted cercarije are 

 also often found in these, although almost any other inverte- 

 brate, or even a fish, may serve as hosts for them. 



Although numerous Trematodes are to be found, it is not 

 by any means every mollusk that is infested. For instance, 

 out of 200 Pufpura lapillus from Fenham Flats only two were 

 found to have these parasites in them|, but on the other hand 

 over 60 per cent, of Palndestrina stagnalis were infested by 

 some kind of Trematode ; sometimes two species in one 

 specimen. 



* See Northumberland Fisheries Report for 1904-5. 

 t See Annals and Magazine of Natural History, January, 19074 



