278 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



INTERNAL PARASITES AND DISEASED 



CONDITIONS OF FISHES. 



By Jas. Johnstone. 



Trematoda. 

 Distomum {?) valdcinflatnm, Stossich (Pis. IY.,Y., figs. 9, 10, 



14 and 15). 



(From muscles of Pleuronecies limanda.) 



One of the fishermen* who attended the Piel Classes 

 in the spring of 1904 told me that, about that time, many 

 dabs caught in the neighbourhood of Blackpool were very 

 thin and emaciated, and had white spots in their flesh. 

 Suspecting the presence of sporozoan parasites, I asked 

 Captain Wignall to try and procure me a few specimens 

 of the fishes in question, and in the course of a week or so 

 I received from him about half a dozen smallish fishes, all of 

 which were infested with some kind of parasite which gave 

 the flesh, in some cases, the appearance of "measly pork." 

 One or two specimens in particular were badly infected, 

 and were very thin indeed for a dab at the end of the 

 spring. Iu November, 1904, again, while trawling in 

 Luce Bay, quite a number of dabs were seen to be infected 

 in the same way. These fishes were mostly small (8-11 

 inches in length, but in one or two cases large dabs (10-13 

 inches) were also infected, though it was only here and 

 there along the bases of the median fin that the parasites 

 could be seen. 



The parasites were situated in cysts, mostly just 

 underneath the skin in the superficial muscular tissue, 

 and principally on the blind side of the fish. They were 

 most numerous along the bases of the dorsal and ventral 

 fins, and were found even between the rays of these fins. 

 Sometimes they were very noticeable, shining with a kind 

 *Mr/J. K. Parr, of Blackpool. 



