356 ULCER DISEASE OF RAINBOW TROUT, 



ulcer-producing function while under artificial conditions of 

 culture. There is, therefore, reason to believe that Micrococcus 

 pyogenes is the cause of the disease in salmon trout, characterised 

 by the production of ulcers, and • that its specific pathogenic 

 action is influenced by an unhealthy or low condition of the fish 

 such as might be caused by an insufficient water suppl}'- and the 

 overcrowding of the tanks. 



There is the doubt that the production of sores and ophthalmia 

 are induced by two different agents. The reasons for believing 

 this are —(1) One carcase seldom shows both types of lesion; (2) 

 fishes die of ophthalmia at times when no ulcers are found upon 

 other trout; (3) Micrococcus pyogenes could not be isolated from 

 those cases of ophthalmia which did not show the ulcers; and (4) 

 the ulcer disease is known in other localities, and in describing 

 the disease writers make no mention of ophthalmia. 



In a report upon an epidemic among brook trout {Salvelinus 

 fontinalis) on Long Island, Calkins"^ describes a disease which 

 appears to be identical witli the ulcer disease of rainbow trout. 

 His photograph of the diseased brook trout shows an appearance 

 precisely similar to that which I saw on the rainbow trout. He 

 did not examine the carcases bacteriological^, but as the result 

 of many observations upon sections of the organs of diseased 

 fishes made after imbedding in paraffin, Calkins concluded that 

 the disease was caused by a new sporozoon which he named 

 Lymphosporidium truttce. The plates which are reproduced in 

 his paper show spores 2 ^ in diameter, and he mentions sporo- 

 zoites 0-5 /x in diameter. The micrococci which I found might 

 simulate these sporozoites. In the milt of diseased rainbow 

 trout forms were met which at first sight appeared to be 

 Calkins' spores, but these proved to be the bodies of the sperma- 

 tozoa. The similarity between Calkins' spores and the bodies of 

 the spermatozoa is remarkable. They both stain deeply with 



* Fourth Annual Report of the Commissioners of Fisheries, Game and 

 Forests of the State of New York, 1898. 



