On the Internal Parasites of the Tweed Salmon. 115 



EXPLANATION OF PLATE IV. 



Fiff. 1. Hana Ansorgii, p. 107, natural size. 

 Fig. 2. Arthroleptis xenochirus, p. 108, natural size. 

 Fig. 2 a. Arthroleptis xenochirus, lower aspect of hand, X 4. 

 Figs. 3, 3 a. Arthroleptis parvulus, p. 109, natural size. 

 Fig. 3 6. Arthroleptis parvulus, lower aspect of foot, X 4. 

 Fig. 4. Psammophis Ansorgii, p. 113, upper and side views of head and 

 anterior part of body, natural size. 



XI. — On the Internal Parasites of the Tweed Salmon. Bj 

 James R. Tosh, M.A., D.Sc, Assistant Professor and 

 Lecturer on Natural History in the University of 

 St. Andrews. 



[Plate v.] 



Specimens of the parasites mentioned below were collected 

 during the net-fishing season of 1895 at the premises of the 

 Salmon Fishing Company, Berwick-on-Tweed. 



The distinctly marine character of the parasitic guests of 

 the salmon is au indication of the nature of its food. Fresh- 

 water parasitic forms are very rare in the salmon, and the 

 fact that they are practically absent in well-grown fishes 

 seems to point to the conclusion that salmon do not feed in 

 the liesh water of a short river like the Tweed except under 

 extraordinary conditions, when a prolonged stay is imposed 

 upon them. 



The following is a list of Entozoa observed : — 



Ascaris capsularia, Rud. Echinorhynchus angustatus, Rtid. 



acuta, Milll. Bothriocephalus iufundibuiilbrmis, 



obtusocaudata, Zed. Rud. 



Distoma varicum, Rud. Tetrarhynchus grossus, Rud. 



ocreatum, Rud. macrobothrius, Rud. 



Miescheri, Zschokke. Tetrabothriuni miuinnim. Larva. 



Echinorhynchus acus, Rud. sp. Larva. 



proteus, Westrumh. Taenia sp. Larva. 



Ascaris capsularia^ Rud. Entoz. t. ii. i. p. 179. 



This form occurs very plentifully encapsuled on the pyloric 

 caica and mesenteries. The average length is about 26 nun. 

 It is very active when taken out. The usual infection is 

 from 20 to 50 in each fish. 



Ascaris acuta, Miill. Zool. Dan. vol. iii. p. 53. 



This is the parasite that occurs most frequently in the 



