Moore. — New Species of Parasite in Trout. 85 



the entire hatchery. In hatcheries where fish are kept through 

 the winter, it would be highly desirable, if possible, to make a 

 rigid separation between the younger and older fish, and, under 

 no circumstances, to permit any implement or utensil used in 

 connection with the older fish to be used or brought into the 

 building where the younger fish are to be raised or are kept. 

 For instance, at Cold Spring hatchery, nothing used in connec- 

 tion with the outside races should be permitted to be brought 

 into the hatchery building and the hatchery building should be 

 put through the course of sterilization above mentioned. There 

 is no doubt but that the adult fish at these hatcheries harbor the 

 disease, so that danger of reinfection of the rearing troughs must 

 always be present. 



IMPORTANCE OF THE STUDY. 



Because of its prevalence octomitiasis is unquestionably a 

 disease of considerable economic importance. The vested in- 

 terests in state, federal, private and commercial hatcheries de- 

 voted to trout rearing are extensive and their combined losses 

 enormous. The greater susceptibility of brook trout over other 

 species limits the output and jeopardizes the future culture of 

 this favorite game fish. 



The study of this disease is still in its initial stages, the 

 work of a single season, and much remains to be done before a 

 definite mode of treatment can be prescribed. Further study is 

 essential on the morphology of the organism, on its mode of in- 

 crease, its transmission and the general or special conditions af- 

 fecting its pathogenicity. 



Aside from the benefits to be derived from this study in the 

 field of fish culture, there are those which are directly applicable 

 to human problems in the field of comparative medicine. For 

 example, Octomitus in the fish and Giardia in man are closely 

 related protozoa. Both are octo-flagellates that parasitize their 

 hosts in the intestine with attendant symptoms of dysentery. It 

 has been noted that in case of infected fish Octomitus penetrates 

 the wall tissue of the intestine where it passes certain of its de- 

 velopmental stages, and that in cases of heavy infection such 

 parasitism is accompanied by a general disintegration or break- 

 down of tissue resulting in the fatal sickness. Observations of 

 this kind, as shown by Octomitus, should throw light on the 



