A. E. Shipley 
281 
Zschokke 1 tells us that together with Dibothriocephalus infundibuli- 
formis and the nematode Cucullanus elegans, T. nodulosus is one of 
the commonest of helminthes found in the fish of the Lake of Geneva. 
Like the first named of the above three worms it occurs in many species 
and in many individuals of those species. It further occurs all the year 
round. The cysts contain larvae in various stages of development. 
The cysts usually occur in the liver but they have also been found in 
the spleen, the muscles of the tail and in the walls of the intestine and 
in the body cavity, these last two situations harbour larvae in very early 
stages of development. They occur in some numbers, as many as thirty- 
six having been recorded from the same fish. 
These larval forms attain at times a surprising length. Ordinarily 
from one to three centimetres long they have been found encysted in 
the tail muscles, eight, fifteen and even twenty-five centimetres in 
length. 
These cysts have also been found in the tissues of the pike (Esox 
lucius L.) the normal host of the adult T. nodulosus, in the grayling 
(Thymallus vulgaris Nilss.), in the trout ( Trutta variabilis ) and in the 
salmon ( S. nubia), but in the grayling, the trout and the salmon they 
attain very small proportions Cysts have also been described from the 
pope fish ( Acerina cernua L.). 
The adult form normally inhabits the duodenum of the pike and 
lies with its head firmly fixed in the walls of the alimentary canal. It 
has also been found, though much more rarely, in the intestines of the 
fishes mentioned above. 
1 Arch. Biol. 1884, v. p. 153. 
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