214 American Fisheries Society 



species exist in this country, I cannot doubt, in view of my 

 own experience. In several cases I have seen infections of 

 Myxosporidia which could not be identified as known species. 

 These forms should receive careful attention with a view to 

 determining fully the species present in this country, together 

 with their frequence, their range, and the factors which de- 

 termine their occasional serious increase in numbers. 



A related form which also belongs in this subdivision is 

 the organism that produces an epidemic among brook trout, 

 Lymphosporidium truttce. The minute spores are found in 

 all organs, and sharply limited deep ulcers appear on the fish 

 and extend into the internal organs. These epidemics are ex- 

 tremely fatal among brook trout of all ages. The parasite 

 has been carefully studied by Calkins, who inclines to the 

 view that the fish may not be its original host, as similar or- 

 ganisms are found in the body cavity of various small Crus- 

 tacea and the trout become infected by swallowing such Crus- 

 tacea containing the Protozoa. The method recommended 

 for handling this disease includes the destruction of diseased 

 fish, the draining of infected ponds, and their exposure to the 

 sun. If interbreeding of diseased fish is avoided and the 

 water kept clear and cool as well as other means taken to 

 sustain the vitality of the fish and prevent deterioration 

 through inbreeding, the disease can be kept under. Marsh 

 has recommended that the fish culturist avoid over-crowding 

 and transfer diseased fish to larger quarters with more rapid 

 flow of water. The disinfection of ponds by chloride of 

 lime or copper sulphate appears to be of value. 



Among the flagellate protozoans there are only two. 

 forms which call for more than passing consideration. The 

 species known as Costia necatrix produces a serious and 

 well-characterized disease among trout, goldfish, and other 

 aquarium inhabitants. The skin of the fish loses color and 

 becomes cloudy in spots. This effect is due to the assem- 

 blage at the surface of an enormous number of the micro- 

 scopic flagellates. They are usually anchored to the skin by 

 their long flagella. Treatment of the fish with two per cent 



