32 TREMATODES OF THE NORTHUMBERLAND COAST 



consequence generally colourless. The lobes reach not quite 

 to the level of the centre of the ventral sucker. The excretory 

 vesicle is clear and somewhat horseshoe-shaped. The repro- 

 ductive organs are in part well developed, a pair of oval testes 

 lying one each side of the excretory vesicle, and reaching to 

 the level of the centre of the ventral sucker. The ovary lies 

 just in front of the right testis : it is also oval and slightly 

 smaller than that organ. The vitellaria lie below and to the 

 side of the ventral sucker. They consist of two roundish 

 masses of very opaque cells, each giving off a short and rather 

 thick duct which runs forward and unites with its fellow just 

 in front of the ventral sucker. I might mention here a peculiar 

 structure noticed in one or two of the specimens immediately 

 in front of the ventral sucker (see fig. 2, X.) It looked like 

 an oval aperture with a rim and muscles radiating from it. It 

 was not , to be seen in preserved specimens, and I am at 

 present unable to account for it. 



This cercaria does not agree with any known species of 

 Gytnnophallns ; in relative size the suckers differ from those of 

 all the others. It appears to be nearest to Ni coil's G. dapsilis 

 mentioned above. The forward position of the vitellaria is 

 rather similar, but the ventral sucker in the present species is ; 

 smaller in relation to the oral sucker. 



This worm was found in three specimens of Macoma balthica 

 out of about twenty examined. 



Cercaria strigata (Plate I. fig. 3.) This cercaria, 

 previously referred to Brachyc«lium luteum, is now considered 

 by Giard to be the larval stage of Gymnophallus somatertcB, 

 Levins. It occurs very commonly in Tellina tenuis and rarely 

 in Donax vittatus, both from Alnmouth. These mollusks are 

 often cast up alive on the beach, and most probably are much 

 eaten by the sea-birds which feed there. The Eider Duck, 

 however, is not common there, and if it ever comes is a rare 

 visitor, whereas it is frequent on Fenham Flats. 



Having found this worm abundantly since first recording it 

 from Northumberland, I arr, now able to give a more correct 



