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Part III. — Twenty-sixth Annual Report 



Several young specimens of a Distomum, which closely resemble 

 the immature D. cestoides from the Skate, were found encysted on 

 the walls of the stomach of a Witch Sole, Pleuronectes microcephalus, 

 captured in the Moray Firth. There were several cysts observed, and 

 all those examined contained only young Distomids — in some cases one, 

 in others two examples. Two of the young forms and one of the cysts are 

 shown on Plate VII., figs. 5 and 6 ; the figures are about twice the natural 

 size. 



Fishes form a considerable proportion of the food of large Skates, and 

 probably the Witch Sole, which lives in moderately deep water, some- 

 times becomes the prey of these large Plagiostomes, Should this happen, 

 the encysted Distomids will be liberated and reach maturity in the 

 alimentary passages of their new host. 



Several other large Distomids besides the one here referred to have 

 been recorded as the parasites of various fishes. One of the largest, 

 perhaps, was that obtained by Nardo in 1827, from a fish captured in the 

 Gulf of Venice. Two specimens of this parasite were obtained, one of 

 which measured five inches in length.* This species was named by Nardo 

 Distoma gigas, but Dr. Cobbold, the English authority on Entozoa, 

 considered that Nardo's Distoma belonged to the same species as that 

 described by Rudolphi in his history of Entozoa published in 1808, under 

 the name of Distoma clavatum* The species described by Creplin as 

 Distomum veliporum is also a moderately large one. It is said to attain 

 a length of three inches, and as it has been recorded from the same 

 species of Skate as those described above,t I was at first under the 

 impression that those found by me might belong to that species. 



Our specimens, however, agree better with van Beneden's figure in his 

 work Les Poissons des cotes de Belgique, p. 17, PI. IV, fig. 9., than with 

 the description of D. veliporum in Diesing's Systema Helminthum. 

 I have therefore provisionally ascribed our specimens to van Beneden's 

 species Distomum cestoides. 



It may be noted here that D. veliporum is apparently a widely-dis- 

 tributed species. Prof. E. Linton, of Washington and Jefferson College, 

 U.S.A., has described in the proceedings of the U.S. National Museum 

 (vol. xx., p. 521) a large Distomum from the stomach of a "Barndoor 

 Skate," Raia loevis, captured at Wood's Hole, Massachusetts, which he 

 ascribes to this species. This specimen, however, like that of D. cestoides 

 recorded by van Beneden, was incomplete. The specimen recorded here 

 is in fairly perfect condition. 



Cestoda. 



Genus Bothriocephalus, Rudolphi (1808).. 

 Bothriocephalus proboscideus, Rudolphi. PI. V., fig. 4. 



1 808. Bothriocephalus proboscideus, Rud., Entoz. Hist. Nat., 

 vol. ih\, p. 39. 



1850. Dibothrium proboscideum, Dies., Syst. Helminth., 

 vol. i., p. 590. 



This Cestode was obtained in the intestine of a Trout captured in Loch 

 Tay, in August 1901, by my colleague, Dr. H. C. Williamson. The 



*See "Parasites," by T. Spencer Cobbold, M.D., p. 460; and " Systema 

 Helminthum," Diesing, voi. ii., p. 366. 



t Catalogue des Poissons des cotes de la Manche dans les environs de Saint- 

 Vaast, par M. A.-E. Malard. Bull. Soc. Philomathique de Paris, 8 ed., Ser. t. II., 

 p. JO (1890). 



