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Some Parasites of Sagitta bipunctata. 
By 
d 
Marie V. Lebour, M.Sc., 
Assistant Lecturer in Zoology, Leeds University. 
Temporary Naturalist at the Plymouth Laboratory. 
With text Figures 1-6. 
Sagitta has been several times noticed as a host for various parasitic 
worms, notably a larval nematode and several trematodes. Larval 
cestodes have also been seen in it. It is exceeding voracious and ap- 
parently eats almost any animal food, especially its own species and 
small crustacea, so that it is not to be wondered at if it forms a con- 
venient intermediate host for many worms, and as Sagitta itself is an 
important fish food it naturally follows that the adults of these parasitic 
worms are usually found in fish as their final hosts. So far, however, the 
hfe histories of the larval forms hitherto found have not been deter- 
mined, so we are pleased to be able to identify two trematodes belonging 
to well-known species which inhabit Sagitta as intermediate host and 
fish as the final host. 
Busch (1851) and Leuckart and Pagenstecher (1858) have described 
several larval trematodes and a nematode from Sagitta, Ulianin (1871) 
a nematode, and Pierantoni (1913) a nematode. The latter nematode is 
probably the same worm found in Sagitta in Plymouth Sound. Busch’s 
description of a nematode in Sagitta is too vague to recognise it, and 
unfortunately Ulanin’s paper has not been available for reference. 
Leuckart and Pagenstecher mention two larval trematodes from Sagitta 
germanica (=Sagitta bipunctata Q. and G.), one a monostome and the 
other a distome. Although these are figured, they are neither described 
nor named. The distome (Plate XXI, Fig. 9) is probably the larval 
Derogenes varicus which occurs in Sagitta bipunctata in Plymouth Sound. 
Busch’s trematode larve found in Sagitta cephaloptera (=Spadella 
cephaloptera) were identified by him as Distomum papillosum Diesing 
(=Distomum beroé Will (1844)) and two new species, one of which he 
names Distomum fimbriatum and the other Distomum crassicaudatum. 
Distomum papillorum appears to be a larval Hemdurus, D. fimbriatum 
