G. H. Drew 
195 
For an account of the literature of the subject see Gurley, R. R. 
(1894). The Myxosporidia or Psorosperms of Fishes. Commissioners’ 
Report of the United States’ Commission of Fish and Fisheries for 1892. 
Part XVIII. p. 194. 
On bacterial infection accompanying the invasion of the swim 
bladders of trout by Cystidicola farionis (G. Fischer). 
Some Rainbow and Brown Trout belonging to the Hon. Sydney 
Holland, Royston, Herts., have for some time been dying in considerable 
numbers with symptoms of an infection of the swim bladder. 
Shortly before death they are found swimming near the surface of 
the water and finally die with their heads downwards and body nearly 
perpendicular. The swim bladder in every case was infected with the 
threadworm Cystidicola farionis. The condition has been fully described 
by Mr A. E. Shipley in his Note on Cystidicola farionis [Fischer] 
(.Parasitology , Yol. I. June 1908, pp. 190-192). 
Some of these trout were preserved in formalin and sent to me 
for examination at the Plymouth Laboratory of the Marine Biological 
Association. 
In every case from 10 to 30 specimens of Cystidicola were present 
in the swim bladder, and in many cases a small amount of a fibrino- 
purulent material was adherent to the walls. Smears of this exudation 
were made, fixed by heat, and stained with methylene blue. Under 
the microscope these slides showed many leucocytes, fibrin, and large 
numbers of bacteria. The leucocytes were somewhat degenerated but 
many of them showed phagocytosis: many different forms of bacteria 
were present. Preparations of the walls of the swim bladder showed 
dilatation of the capillaries with transmigration of leucocytes and some 
fibrin formation. The condition was typically that which would be 
produced by infection of a serous cavity with bacteria. 
Through the kindness of Mr Holland I was able to go to Royston 
and investigate the matter on the spot. Eight fish were caught and 
dissected, of these seven were infected with Cystidicola. These seven 
all showed signs of inflammation of the swim bladder and smears 
showed the presence of many bacteria and distinct pus formation : 
the remaining fish, a Brown Trout, was free from Cystidicola and the 
swim bladder showed no signs of inflammation nor could any bacteria 
be detected. 
In each case before opening the swim bladder, the wall was well 
13—2 
