136 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



RE-DESCRIPTION OF A TEEMATODE PARASITE, 

 ALLOCREADIUM LABRACIS (Dujardin), 



FROM THE BASS. 



(Plate III.) 

 By J as. Johnstone. 

 Bass or Sea-Perch [Labrax (or Centropomus) lujms) 

 in the Irish Sea are nearly always infested with a Trerna- 

 tode parasite which is evidently the species AUocreadium 

 labracis (Dujardin). This worm, if not of universal 

 occurrence in the fish, is very common, and I have found 

 it in specimens taken in Cardigan Bay, in the Irish Sea, 

 and in Morecambe Bay. The bass is an inhabitant of the 

 Mediterranean and the adjacent Atlantic coastal waters, 

 where it is very abundant. It enters St. George's Channel 

 and the Irish Sea in shoals in the early summer, and in 

 June has reached Morecambe Bay, where there is nearly 

 always a fishery for it during June, July and August. 

 About September or October the shoals disappear. The 

 fish appears to be largely a fish-eater, feeding upon young 

 sand-eels and sprats which are abundant in Morecambe 

 Bay during these months. Although common in the 

 English Channel and the Irish Sea area, the shoals do not 

 migrate much further north, and only isolated specimens 

 are taken on the East Coast of Scotland, north of the Forth, 

 and in Scandinavian waters. The parasite AUocreadium 

 labracis appears to be a good example of a Trematode 

 which has only one final host, as all the descriptions in 

 the literature appear to relate to worms taken from the 

 intestine of the bass. Thus Dujardin's original descrip- 

 tion of the species was based on a specimen taken from 

 Labrax lupus, and Stossich and Molin described it from 

 the same host.* In such cases as this the occurrence of a 



* The literature is summarised by Odhner in Zool. Jahrb. Abth. System., 

 Bd. 14, 1900-1. I am indebted to Mr. W. Nicol, of the Gatty Marine 

 Laboratory, for directing my attention to this paper, and for other 

 assistance. 



