Preliminary Notice of a Parasitic Copepod. 247 
extending over so considerable an area (40 millimetres in 
length by 10 millimetres in breadth) as quite to alter the 
ordinary appearance of the latero-posterior aspect of the 
thoracic cavity. On closer observation, the deformity was 
seen to be produced by a somewhat worm-like animal, whose 
head was attached to the walls of the vas deferens. This 
parasite, evidently a female, was accompanied by a small 
male of a very dissimilar form, which lay towards its posterior 
margin. I removed these dimorphic parasites from their host, 
and placed them in methylated spirit for future examina- 
tion. On a later inspection of these animals, I recognised 
that neither of these were as well preserved as I would have 
desired, and therefore I set myself the task of finding 
further specimens, and of endeavouring to obtain data as to 
the frequency of their occurrence. For this purpose, all the 
specimens supplied to us for class dissection were carefully 
examined, and, in addition to this, I looked over a number of 
Norway lobsters at a well-known fish-dealer’s in town. 
After an examination of about five hundred specimens, I had 
only procured two more parasites—a male and a female—and 
these not occurring on the same host; but in addition to 
these two actual specimens, in two other cases I noticed a 
degeneration of the vas deferens, possibly produced by a recent 
attack of this parasite. Thus it appears that during the 
winter season this parasite is by no means a frequent guest 
in Nephrops norvegicus, probably only one animal in a 
hundred being infected by this parasitic Copepod. In 1884 
Mr J.T. Cunningham showed that the Norway lobster is 
attacked by a parasitic Trematode, which he named Sticho- 
cotyle nephropis, which lives in the rectum of its host ; and it 
is interesting to note that these Trematodes are much more 
frequent in occurrence than is the case with these Copepod 
parasites, for Cunningham says, “ Usually out of a dozen 
opened, three or four are infected.” On the other hand, my 
percentage is the same as that given by Nickerson for the 
infestation of another host—the American lobster—by the 
same Trematode, Stichocotyle nephropis. The more general 
haunts of parasitic Copepoda are the skin, scales, muscles, 
fins, gills, eyes, lips, tongue, nasal cavity, and palate, and 
