SEA-FISHERIES LABORATORY* 295 



INTERNAL PARASITES AND DISEASED 

 CONDITIONS OF FISHES. 



By J as. Johnstone. 



1. CESTODA. 



2. TREMATODA. 



3. FUNGI. 



4. TUMOUR FROM SKIN OF DAB. 



I am describing here a small collection of cestodes 

 and trematodes made last summer from trawl fish caught 

 by the s.s. " John Fell." As a rule the species collected 

 were taken from skates and rays. The usual method of 

 collection was to take the whole gut from the fish to be 

 examined and place it in a dissecting dish containing 

 fresh water. The gut was then slit up longitudinally and 

 examined bit by bit. In a short time the fresh water 

 causes the worms to relax and they can then be detached 

 from the intestinal wall without injury to suckers or 

 hooks. If they are kept in fresh water for about a 

 quarter of an hour complete relaxation takes place before 

 death, and in the case of cestodes bothria are expanded, 

 while with trematodes the animals die without any trace 

 of wrinkling. In the case of the latter animals it is 

 always necessary to make stained preparations in order to 

 determine the species and this is greatly facilitated by 

 gently pressing the worm, while alive, between a slide 

 and cover glass, or between two slides, according to its 

 size. The whole is then put into a flat dish containing 

 fresh water and in a short time the animal dies in a 

 beautifully fiat and thin condition. I have found that 

 about 5 per cent, formalin makes the best general preserva- 

 tive for cestodes if it is desired to display the animals in 



