452 LARVAL TREMATODES OF THE NORTHUMBERLAND COAS'J'. 



Lophivs piscato7-his. Mr. Tennant found the adult in the Gar 

 Tylosuriis marimis and the encysted stage in the Silverside 

 Menidia vieuidia : he however doubts if it is necessary for the 

 worm to encyst in a fish different from its final host. He is 

 also of the opinion that the freshwater Gasterostomum 

 fimbriatinn and its larval form Bucephalus polymo7phus are 

 identical with G. gracilescens and B. hainieanus, and gives 

 various reasons for this view. The theory that a marine and 

 a freshwater form can be identical is borne out by the fact 

 that I have found Monostomum flavum and M. lophocerca in 

 Pahtdestrina stagualis when their usual hosts are true fresh- 

 water Gastropods. Cobbold"^' found Gasterostoimim gracilescens 

 in Lophius piscatorius — presumably from Britain, although he 

 does not say so — and figures it. This is probably the final 

 host on this coast, as it is common. Maddox found it 

 encysted in the nerves of the common Haddockj, and I have 

 found it in the nerves of this fish from the Northumberland 

 coast. It has also been found by Mr. Johnstone in the 

 Gadidae of the Lancashire coastj. Giard found it encysted 

 in Belone vulgaris, and this fish used to be very common at 

 Budle, where there was a special fishery for it, but now it is 

 rare. 



Bucephalus haimeanus is found in long winding and branch- 

 ing sporocysts, in my specimens so long and tangled together 

 that one could hardly find out where they began or ended. 

 These fill up the visceral cavity, completely destroying the 

 gonad, riddling the liver, and enveloping the intestines. The 

 whole animal of the cockle looks whitish, and long strings of 

 sporocyst can be pulled out of it (see Plate XIII. A). Inside the 

 sporocyst are the Bucephalus cercariae in all stages of develop- 

 ment. Young ones have short tails, and show not much more 

 than a large excretory sac (see Plate XIII. C). The full grown 

 cercaria (A) is about 0*26 mm. long without the tail — slightly 

 larger than the American specimens, which are o'i5 to o'2o 



* Trans. Linn. Soc, London, XXII., 1858, p. 16L 



t Qnai-t. Joiirn. Micr. Sci., VII., 1867. 



X Op. cit., p. 101. 



