J. Johnstone 
365 
the flesh. In three of these cases the muscles of the flesh of the fishes 
— a Halibut, a Megrim and a Hake—contained cysts which enclosed the 
larvae of a Tetrarhynchid, and on examination the latter was identified 
as T. erinaceus from the peculiar nature of the armature of the 
proboscides. In another case the wall of the stomach of a Halibut was 
also infected with the same larvae. Acting on an obsolete principle of 
Border Law the Fish Inspectors promptly condemned the fishes and 
then caused them to be examined. I do not think tliere was any valid 
reason for the condemnation of the articles of food, for I can find no 
reference in the literature to the presence of Tetrarhynchids in the 
human alimentary canal, and there does not appear to be any question 
of a possible communication of a parasite by the consumption, as food, 
of such infected flesh. Further the number of larvae present was far 
too fejiV to lead to any emaciation of the fishh or to the likelihood of the 
production of toxic substances in the flesh of the animal. Nevertheless 
the Inspectors probably acted in the interests of the public health 
in condemning such articles of food as contained obvious cyst-like 
structures in the flesh, as to the precise nature of which they were 
ignorant, since there is always the possibility that these bodies might 
be detrimental to the health of those eating them. Further the 
presence of the cysts was very obvious and rather unpleasant to the 
eye, and might easily have prejudiced a customer against a particular 
vendor, or fish. However this may be my attention was thus directed 
to the Cestode and it was found that it was widely distributed in Irish 
Sea fishes. On searching the literature I also found that though there 
are many mentions of the occurrence of the worm there is no detailed 
description of its structure; and it seemed that an adequate investiga¬ 
tion of this interesting form might be of considerable importance. The 
present paper is therefore the first instalment of such a study. 
II. Distribution and life-history. 
Tetrarhynchus erinaceus appeal’s to have first been described by 
P. J. van Beneden in 1850 from the Angler-Fish (LopJdus piscatorius) 
and the Cod (Gadus callarias) in which fishes it was present as encysted 
larvae ; and from various species of Rays where it was present in the 
sexually mature phase (van Beneden 1858). The same author has also 
^ Such an emaciation as I have observed to result from the infection of a fish by the 
larvae of a Trematode worm; see Johnstone (1905); Nicoll (1909); and Lebour (1907). 
