Moore. — Study of Trout Diseases. 



77 



of food and they afford excellent material for observing how 

 serious the infection may be when they are free to range over 

 wild waters, where natural food is available. 



In these situations the adult brown trout and fingerlings 

 carry the organism in varying degrees of intensity, seemingly 

 quite unaffected by it. It is a question, however, how long 

 they can tolerate such severe infections as have been observed 

 without becoming so devitalized as to succumb either to this 

 or some other disease. In the stream where the browns were 

 most heavily parasitized no brook trout were found and the 

 local comment is that they are now never found there. Of 

 course the explanation of their extermination from the stream 

 they once inhabited may lie along one or more lines, either 

 they die of the disease or they are driven out by the browns 

 and rainbows which now populate the stream. Probably both 

 factors operate in their extermination. Infected brook trout, 



Fig. 1. — Diagram ilhutrat.ing a section of the digestive tract of trout in typical 

 infection by Ociomitits salmottis. The orf,'anism in its various staeres appears in 

 heavy lines in Groups A-F. Group A, segment of germinating spore and juveniles : 

 Group B. n uit witi; ;!• icat-fn. hy z:-. :i>\\- . mi binary ft^i.i. ./r; of i.cvelopnieDtHl 

 sta??es of Errowth within the epithelial ce!h- of ceca anl fore-inte-tine. D, in.'icatinfr 

 multiple fission; Group E, stages concerned in the development of a resistant spore; 

 Group F, juveniles attached to a blood corpuscle. 



