73 U. S. BUREAU OF FISHERIES 
lengths of time. The value of these concentrations in preventing 
certain diseases was then tested at producing hatcheries by means 
of routine 1-hour applications at weekly intervals. 
During the course of the experiments, which extended over a 
period of 3 months, a serious outbreak of the Western type of gill 
disease occurred at the Birdsview (Wash.) Hatchery, and a mild 
outbreak at the Quinault hatchery. Prolonged treatments with 
malachite green, potassium permanganate, and chlorazene failed 
to exert any beneficial effect in preventing the disease. A consider- 
able drop in the mortality followed treatments with copper sulphate 
and boric acid, but further experiments with both chemicals will be 
necessary before any conclusions concerning the prophylactic or 
therapeutic values of these disinfectants are justified. 
During 1938 a new technique was developed for treating fish in 
relatively large volumes of water, such as are found in circular 
pools and in raceways. In this method the water supply to the 
pond is shut off and the amount of predissolved disinfectant nec- 
essary to attain the desired concentration is added. The water is 
kept mixed and aerated during the treatment by means of a 
centrifugal pump. 
After completion of the new laboratory at Quilcene, a series of 
controlled infection experiments with the protozoan parasite Cyclo- 
chaeta were initiated. The purpose of the experiments was not only 
to trace the development of the disease under controlled conditions 
but primarily to determine the relationship between daily losses and 
the actual degree of infection present. The results indicate that 
while daily losses are by no means an accurate index of the degree 
of parasitism, and are unsuitable for experimental purposes, they 
are sufficiently accurate to serve all practical purposes. 
Pathological studies on Henneguya salminicola, a myxosporidian 
parasite in the body musculature of several species of Pacific salmon, 
and similar studies on Myxobolus inornatus n. sp., a mMyxosporidian 
found in the body musculature of the black bass, were completed and 
the results prepared for publication. 
At the Leetown station E. W. Surber completed a study of a peri- 
trichous ciliate of the genus Scyphidia, which occurred in large num- 
bers on the gills and bodies of black bass at this station. This para- 
site was discovered on a lot of largemouth fingerlings which sud- 
denly stopped feeding. No attempt was made to control the infec- 
tion and within a few days the fish suffered a sudden and almost 
complete mortality. Although a few Dactylogyrus and Cyclochaeta 
were also found on the fish the Scyphidia are believed to be the prin- 
cipal cause of the mortality. This is borne out by the fact that the 
same pond contained numbers of golden shiners which were more 
heavily infected with Dactylogyrus than the bass, yet suffered only 
a sheht mortality. No Scyphidia, however, could be found upon 
these fish. 
Dr. Davis continued his studies on a suctorian parasite of the 
smallmouth black bass which has been the cause of considerable 
mortality at Leetown among bass of all ages. This parasite is evi- 
dently widely distributed, since it has been found at several hatcheries 
in New York, New Jersey, and Maryland. 
The “Disease Service” continued to function during the past year, 
about the same number of specimens being received for diagnosis as 
