Larval Trcmatodes. 241 



A point of interest is that M'Intosh apparently met with 

 some of tlie single-walled cysts already referred to, for he 

 says (p. 202) that the wall of tlie cysts '^ consists of two 

 layers marked by minute stride and specks ; but the outer 

 cannot always be seen.''' 



Reference may here be made to Miss Lebour^'s investi- 

 gations* of larval Trematodes in Carcinus mcsnas (\om. the 

 Northumberland coast. Her results a|,pear to differ entirely 

 from ours, for although she found the crabs fairly well infected, 

 the cysts were of quite a different character, being single- 

 walled and oval. The cercaria? in these cysts are apparently 

 of the Spelotrema type. Their identity is doubtful, but it 

 seems certain, at least, that they are not the same as the 

 cercarise we have just described. Miss Lebour, however, 

 found a single specimen of another cyst in the crab. This 

 was smaller than the others, spherical and double-walled. 

 The cercaria was not examined, but from the size and 

 character of the cyst it was presumed to be probably the 

 same as M'Intosh had found. Whether this be the case or 

 not it is curious that these double-walled cysts should be so 

 rare in the Northumberland crabs in contrast to their great 

 abundance at St. Andrews. It may possibly be regarded as 

 an instance of the peculiar effect which local conditions may 

 exert even on the parasitic fauna. 



It may not be out of place to mention here another cercaria 

 found by ]\liss Lebour f in Balanus halanoides and referred 

 with much doubt to Spelotrema excellens as the adult. The 

 size (1 mm.) of the cercaria is suggestive of Sptl. excellens^ 

 but the contiguration of the alimentary canal differs con- 

 siderably from that in Spel. excellens and bears n)uch more 

 resemblance to that of Levinseniella brachysoma (Crepl.). 



Cercaria livioiy nov. 



Five specimens of Lima hians were examined and in two 

 of tliem a single cyst was lound. In both cases it was loosely 

 attached to the inner side of the mantle-edge, projecting into 

 the mantle-cavity. 



The cysts are spherical, about "S mm. in diameter and have 

 a thin, opaque, membranous wall. The liberated ceicaria is 

 '6 mm. long and of somewhat elongated oval outline. It is 

 colourless and very transparent, so that little of its internal 

 anatomy could be made out. The suckers are both globular, 



* " Trematodes of the Northumberland Coast : II.,'' p. 10, pi. i. 

 figs. 8, 9, iti Trans. Nat. Hi.st. Soc. Northumberland, New Series, ii. part i. 

 t Lvc. cit. pi, i, figs. 6, 7. 



