teria have been placed in an iodine solution directly on a microscopic 

 slide and the organisms continued their activities, apparently 

 unaffected in the slightest degree. 



The same was true in the case where local lesions were treated 

 with this solution, the organisms showing no effect of the germicide. 

 The preparation of a vaccine or an antitoxin, although proved to be 

 effective, would be out of the question because of the impossibility 

 of application due to the size and number of the fish that would 

 require the treatment. 



In the above investigations the work has not been carried far 

 enough to prove anything definitely, and the results of our observa- 

 tions are given simply as food for thought, with the feeling that 

 others may be sufficiently interested to carry on further experiments, 

 eventually of great value to fish culture. 



But in view of all these facts, the writer is of the firm opinion 

 that the diseases that prove to be the most disastrous are those of 

 bacterial origin, and, owing to their nature, mode of transmission, and 

 apparent resistance to recognized germicidal agents, can only be con- 

 trolled by the creation or rather development of an immune strain of 

 fish. Fish in the native streams as far as we know are immune to 

 these diseases. This immunity has been developed naturally and there 

 is no reason why this condition among fish in our hatcheries cannot be 

 developed artificially by subjecting them to the disease in question 

 and breeding from the survivors of each succeeding generation. In 

 view of the present facts this seems to be the only solution of the 

 problem. 



109 



