OBSERVATIONS AND EXPERIMENTS ON SAPROLEGNIA INFESTING FISH. 



BY G. P. CLINTON, B. S., 



Assistant Botanist, University of Illinois. 



The fresh-water fish in the aquarium of the U. S. Fish Commission at the World's 

 Fair having been more or less troubled by a fungous disease, the writer was asked in 

 October to make a study of the same. A glance in the microscope at material 

 taken from a diseased fish was sufficient to determine that a common fish-pest, Sapro- 

 legnia, was at work; but as it was not present in its mature stage, further study, 

 including culture experiments, was undertaken. 



The fresh-water fish occupied twenty-eight tanks, just within the wall of the cir- 

 cular room, and also a number of larger tanks, separated from the former by a wide 

 aisle. In the center of the room a large circular basin was also given up to them. 

 The water was supplied by way of a crib a few miles out in Lake Michigan, and after 

 having its solid matter precipitated by alum and passing through a sand filter it 

 escaped in several small jets into the individual tanks, entering with sufficient force 

 to carry down air bubbles from one to two feet. The water passed off by an overflow 

 at the top, and was not used again, but drained into the lake. The tanks were 

 emptied once or twice a week and cleaned, while the central basin was run down every 

 night and refilled. It was in certain of the smaller tanks that the disease was worst. 

 The fish were brought to the aquarium in the cars of the U. S. Fish Commission, 

 chiefly from the Great Lakes and from streams of the Mississippi Valley or from 

 breeding stations of the Commission. They were carried in water cooled by ice, but 

 the transfer to the aquarium was so managed that the temperature was gradually 

 raised before they were placed in the various tanks. 



According to the statement of the assistant in charge, the fish never showed signs 

 of disease when they arrived. There were no means of regulating the temperature of 

 the water in the aquarium, and at the higher degrees (68° to 74° F.) the development 

 of the fungus seemed to be considerably stimulated. The fish were fed corn bread, 

 liver, beef, or minnows, according to species. 



The fungus developed on all parts of the fish, though perhaps more abundantly 

 or more frequently on the tail, fins, or head. According to the host or stage of 

 infection, it would be limited to small, definite patches, or spread all over the fish. In 

 general it formed a tuft of white threads that radiated out from the body a distance 



163 



