EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
137 
movement only every few hours, an average of 14.25 hours per day, while for the 
same period specimen No. 2 averaged 16.14 hours per day open. At the end of the 
experiment both specimens were gaping wide open and No. 2 had ceased to move. 
Specimen No. 2 had died after 27 days of treatment. Within one or two days more, 
at most, judging from the infrequent shell movements, specimen No. 1 would have 
died. For the purpose of record the latter is considered to have died in 29 days. 
Figure 11.— Graph showing tho records, in hours open daily, of the two specimens employed in 
experiment No. 19 (2.4 parts per 1,000), Compare with the controls (fig. 12) 
At the same time the control specimens Nos. 3 and 4 (fig. 12) averaged 20.61 
and 17.85 hours per day open. Between the 23d and 28th these specimens remained 
closed a large part of the time. It was suspected that a leak between one of the 
experimental chambers and the control chamber had occurred. The level of water 
in the control chamber was raised a little to prevent flow of contaminated water into 
it, and the specimens again behaved normally. After the experiment had been com- 
pleted such a small leak was found to have occurred. A small quantity of the liquor 
Figure 12. — Graph presenting the records of control specimens for experiments Nos. 18 and 19. 
The low records toward the end were due to a leak from one of the aquaria containing liquor 
solution. Compare with Figures 11 and 13, experiments Nos. 18 and 19 
solution had probably seeped through and produced the striking change in behavior. 
That this was due to some unusual condition in the control chamber alone is shown 
by the fact that the records of the experimental oysters show no unusual variations 
during the same period. 
Experiment No. 18 (8.2 parts per thousand ). — The rate of flow of water was 123 
cubic centimeters per minute and that of liquor solution (1:4) 2 cubic centimeters 
per minute, producing a final concentration of 3.2 parts per thousand pure liquor to 
