SEA-FISHEEIES LABORATORY. 127 



INTERNAL PARASITES AND DISEASED CONDITIONS 

 OF FISHES. 



By Jas. Johnstone, D.Sc. 



Contents. 



1. Didymozoon scombri, Taschenberg 



2. Myxosporidian infection in Anarrichas lupus 



3. Ovarian degeneration in a Cod 



4. Epithelioma in a Turbot 



5. Halibut with benign Tumours in the Body Muscles 



6. Fibrosis of the Liver in a Conger 



7. Fibroma in the orbit of a Cod 



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 142 



Didymozoon scombri, Taschenberg. — Plates I and II. 



A number of specimens of this interesting Trematode 

 were found by Mr. A. Scott, when examining small mackerel 

 caught in the Irish Sea just outside Walney Island, in 

 Lancashire. Odhner* has given a very full and accurate 

 account of the anatomy of the animal, all the details of which 

 I have been able to verify. Nevertheless these particular 

 specimens may be worth describing shortly. 



The worms were contained in cysts (1) on the roof of the 

 mouth beneath the pharyngo-branchials : this was the most 

 common situation ; (2) on the basi-branchials ; (3) on the 

 external surfaces of other parts of the gill bars ; (4) on the 

 internal surface of the operculum. Usually the cysts were 

 single ones, but rarely there was a group of them. They 

 usually measured about 4 to 5 mm. by 2 to 3 mm., but one 

 or two were much larger. They were light-yellow in colour 

 because of the eggs within, which showed through the delicate 



* Odhner, T. " Zur Anatomie der Didymozoen t ein getrenntgcschlecht- 

 licher Trematode mit rudimentaren Hermaphroditismus." In Zoologiska 

 Studier tillagnade, Professor T. Tullberg, pp. 309-342, 1 Plate, Uppsala, 1 907. 



