1 88 REPORT OF THE COMMISSIONERS OF 



fresh-water forms which may easily be swallowed by the fish. The present parasite 

 also resembles the form described by Thelohan and Henneguy* as a parasite of the 

 crayfish, and although the spores of the latter do not contain thread capsules the 

 authors regard it as one of the Myxosporidia. On similar grounds the present 

 parasite might be regarded as one of the Myxosporidia. After one fish is affected 

 the epidemic may spread throughout the entire hatchery by secondary infection ; in 

 the case of Myxosporidiosis, Megnin (see Pfeiffer), Pfeiffer, Ludwig, etc., believe that 

 secondary infection is brought about by the extensive fouling of the water by fish 

 corpses, and they recommend careful prophylactic measures such as removal of dead 

 fish and weeding out of infected fish showing external signs of the disease. The 

 most careful precautionary measures, however, cannot prevent a certain amount of 

 contamination of the water from ulcers of infected fish. 



N$ttmmar\r. 



The cause of the disease can be safely assumed to be a minute parasite, Lympho- 

 sporidium truttcc, belonging to a great group of unicellular parasites, the Sporozoa. 

 Its closest allies are the Serosporidia which infest and block up the body cavities of 

 certain fresh-water Crustacea {Cypris, etc.). It forms sporozoites in the digestive tract 

 of the trout; these penetrate epithelial cells and grow to forms similar to those in the 

 intestine. They finally make their way into the lymph spaces and body cavity 

 (probably by amoeboid motion), where they penetrate muscle cells. No cysts com- 

 parable with those of the Myxosporidia are formed, but, as in the Myxosporidia, there 

 is an amoeboid adult stage which forms spores. Primary infection probably takes 

 place by ingestion of the parasite, but whether these are in the free state or are 

 parasites in some other hosts which are eaten as food, could not be determined. 

 Secondary infection undoubtedly takes place by contamination of the water by dead 

 fish and from ulcers on infected fish. 



The cause of the epidemic at this particular time cannot be ascertained. I have 

 every assurance from the director that the water was pure in every respect and never 

 rose above sixty degrees Fahrenheit in temperature, while a constant flow from 

 springs kept it fresh. Furthermore, his statements that interbreeding was not allowed 

 and that fresh material was introduced through eggs and milt from other parts of the 

 State leaves no reason for regarding the epidemic as due to the lack of vitality 

 through this cause. 



Ann. d. Micro graphie, 1890. 



