188 
TREMATODE PARASITES FROM FOOD-FISHES 
OF THE NORTH SEA. 
By WILLIAM NICOLL, M.A., D.Sc., M.D. 
Australian Institute of Tropical Medicine, 
Townsville, Queensland. 
(With Plate XIII.) 
The following observations were made in September, 1908, during 
a short residence at Aberdeen where, through the kindness of Prof. 
J. Arthur Thomson, I was able to deal with a considerable number 
of fishes in the very limited time at my disposal 1 . The investigation 
was intended as a continuation of that already carried out at St Andrews, 
the object being to examine a number of fishes which could not readily 
be obtained at the latter place. There the fishes dealt with were mostly 
littoral forms, but at Aberdeen attention was mainly paid to the larger 
deep-water fish; of these a plentiful supply could be easily obtained. 
A few species were re-examined here. 
In the course of ten days 79 fish belonging to 23 species were 
examined and of these 71, i.e. 90 °/ 0 were infected with parasitic worms 
which were distributed amongst the various classes as follows: 
Trematodes in 40 cases (51°/ 0 ), Cestodes 45 cases (57%). Nematodes 
46 cases (58%) and Acanthocephala three cases (4%). As is usually 
the case in marine Teleostean fishes, the great majority of Cestode and 
Nematode parasites were larval or immature forms. Only in a single 
case (Merluccius merluccius) was an adult tape-worm found. 
In these fishes the frequency of infection was somewhat greater than 
I had previously had experience of, but the intensity of infection, 
measured in terms of the variety of parasites in each host, was 
1 The expenses of this investigation were defrayed by the Government Grant 
Committee of the Royal Society. 
