72 U. S. BUREAU OF FISHERIES 
noy., a gregarine parasite of the mud crab” (to appear in the Journal 
of Morphology). A report is in preparation on the other phases of 
this work dealing with field observations of oyster mortalities in South- 
ern waters, and the effect of the parasite on the functioning of the 
adductor muscle of the oyster. 
EFFECT OF PULP-MILL POLLUTION ON OYSTERS 
The York River Investigations, carried on by Dr. Walter A. Chip- 
man, Jr, and Dro H. 'N. Calderwood, have been concerned with the 
continued search for the chemical or chemicals present in the effluents 
from pulp mills that cause changes in the physiology of oysters. 
This information is of importance in the problem of eliminating 
pulp-mill pollution. Progress has been made in the elimination of 
some fractions as causative agents, and in acquiring some knowledge 
as to the nature of these physiologically active materials. The in- 
vestigations have not as yet progressed to a point where the actual 
causative agents can be definitely identified. As during the previous 
year, the work has heen carried out in cooperation with the Virginia 
Commission of Fisheries, through an allotment of funds. Addi- 
tional laboratory and office space were provided free of charge by 
the College of W iliam and Mary. 
Studies made prior to 1939 showed that effluents that enter the 
York River from the pulp and paper mill at West Point are effective 
in reducing the rate at which water is pumped by oysters. It has 
also been shown that the effluent that has the most active physiological 
effect arises from the making of pulp, and contains cooking liquor, 
weak black liquor, soaps, and foam, in addition to the wash waters. 
The work during 1939 demonstrated that the physiological activity 
of sulfate soap has been due to the black liquor it contained, and 
that the foam is no more than a mixture of soaps and black liquor. 
Samples of black liquor from which the soaps had been removed 
still maintained their potency. Consequently, the work has been 
directed towards fractionation of weak black liquor. The physiolog- 
ically active material of the weak black liquor has been separated 
through procedures involving precipitation, extraction, and selective 
<olution. 
Chemical investigations on weak black liquor samples are being 
continued, with the , object of discovering whether or not there is any 
correlation between the alkalinity and volatile sulfide content and 
the variations in the effect of these samples on oysters. It is hoped 
that the further fractionation of the weak black liquor and the 
analytical analyses of these fractions will supply definite information 
on the chemical nature of the physiologically active material, and 
thus allow steps to be taken leading to elimination of this type of 
pollution. 
A small group of studies were made this year at the request of 
the Naval Mine Depot at Yorktown, Va., to ascertain whether or not 
wash waters resulting from the purification of stored TNT would 
be harmful to oysters and clams if emptied into the York River. 
As a result of the tests made it was found that no harmful effects 
could be expected at the dilutions to be discharged. 
