PROGRESS IN BIOLOGICAL INQUIRIES, 1921. OF 
less than half a millimeter in length, and so translucent that one 
may easily overlook them, 
Some bullheads removed from a quarry pond near the Mississippi 
River died within 24 hours after being placed in an aquarium of 
running water. The early death of these usually most hardy fish 
could be explained only on the supposition that their vitality had 
been greatly diminished by the small and abundant trematodes 
(Gyrodactylus) seattered over the entire surface of the body. Pos- 
sibly many fish in the river are unfavorably affected by these worms. 
Dr. Van Cleave found a species of another genus of parasitic flat- 
worms upon the gills of sunfish, black bass, and channel catfish, but 
it is believed that worms of this genus (Ancyrocephalus) do not 
cause dangerous infestations. 
Very little study has been devoted to the ectoparasitic flatworms 
on this continent, and previously but four species have been reported 
from fresh-water fishes. Much attention has been given them in 
connection with fish culture in Europe. Treatments which European 
writers have recommended are: (1) A one-fourth of 1 per cent solu- 
tion of salicylic acid, in which the fish remains half an hour (Hiibner) ; 
and (2) a solution of 1 part of potassium permanganate to 100,000 
parts of water. The treatments may require modification for our 
species of fish and of parasites. 
Dr. Van Cleave has also described a new genus of trematodes based 
upon specimens taken from the white bass, occus chrysops, collected 
in Iowa, Illinois, and Minnesota. The parasites were found only in 
the digestive tract and at present are ascribed no economic signifi- 
cance. The parasites are not found in Morone interrupta, although 
that species is a close relative of the white bass. He finds, indeed, 
that the trematode parasites of the yellow bass are entirely distinet 
from those of the white bass, although the two related species display 
marked similarity in range, local “preference, feeding habits, and 
food. 
TREATMENT OF ICHTHYOPHTHIRIUS DISEASE. 
One of the most troublesome external parasitic affections of fresh- 
water fishes in aquaria and ponds is due to a microscopic protozoan 
(Ichthyophthirius), which becomes embedded in the skin and sets 
up a violent irritation. H. L. Canfield, superintendent of fish culture 
at the Fairport station, who has conducted experiments in the treat- 
ment of channel catfish heavily infected with the protozoan parasite, 
reports that commercial carbonate of soda in the form of sal soda 
(washing soda) is effective in alleviating the trouble. 
Using a receptacle other than metal to hold the solution, 150 g. of 
sal soda are placed in 4,000 ec. c. of water, in which solution the affected 
fish are dipped. The diseased fish are held in troughs of lively run- 
ning water, which aids in the treatment and facilitates handling. 
Before each treatment the fish are forced to the lower half of the 
trough, where they are separated from the upper half by means of a 
cross screen. The diseased fish are caught in a hand net, immersed in 
the solution until they show signs of discomfort (darting about), and 
then placed in the fresh water at the upper end of the trough. This 
process is continued until a material reduction in parasites is noticed 
