514 



floated to the surface of the water and were removed and thrown 

 away. Some of these had no external marks whatever to indicate the 

 disease, but were plump and apparently sound, the cause of death 

 apparently being some internal organic trouble. Others however, had 

 numerous round clear-cut holes or ulcers in the sides or back; in 

 others great patches of the skin and underlying muscle tissue had 

 fallen out leaving large irregular, but shallow pits sometimes two or 

 three square inches in area; in others the flesh had fallen away in 

 spots leaving the back bone visible, and in others still, the clear-cut 

 holes went entirely through the body wall and not unfrequently the 

 internal organs e. g. the testis or liver could be seen, even in the liv- 

 ing fish, hanging out of the openings thus made. Again the eyes 

 would be entirely gone, or the lower jaw would be eaten away, and 

 many instances were seen in which the tail and one or more of the 

 fins had disappeared. 



In looking over the available literature I could find no record of 

 an epidemic of like nature among Brook Trout. Inquiry however led 

 to the discovery that about twelve years ago a very disastrous epidemic 

 had carried away most of the Brook Trout in a neighboring hatchery. 

 Unfortunately no report was written upon this epidemic and the cause 

 of the trouble was not located. From one or two eye-witnesses I was 

 able to gather that the diseased fish at that time had similar holes or 

 ulcers in the body wall and that various parts were eaten away in a 

 similar manner. I do not doubt that the epidemic of twelve years ago 

 and the one of last summer were due to the same cause. 



A careful examination of the surroundings of the fish left no 

 reason to believe that the disease was due to the external conditions. 

 The water of the ponds is supplied from springs having a constant 

 flow of cold and clear water which is free from suspended matter and 

 rarely exceeds a temperature of 60 degrees F. The bottoms are of mud 

 and gravel with comparatively few weeds. 



On the other hand the wide distribution of the diseased spots 

 about the body of the fish led to the belief that the cause of the trouble 

 lay in some parasite small enough to be carried about in the blood to 

 all parts of the animal. 



The large number of reported cases of Myxosporidiosis in fish of 

 various kinds led me at first, to think that I should find the cause of 

 the epidemic to be some member of the order Myxosporidiida of the 

 Sporozoa. With this in mind the various organs of diseased fish were 

 fixed in different killing agents and carried to the laboratory for exa- 

 mination. The material thus collected consisted of digestive tract, 

 liver, kidney, gall-bladder, testis, swimming-bladder, gills, muscle and 



