EFFECTS OF PXJLP MILL POLLUTION ON OYSTERS 
135 
became less and less active until it remained open and entirely motionless on October 
18. This is characteristic of a dead or dying oyster. A graph (fig. 7) is presented 
to show the slow reduction in the number of shell movements, or adductor muscle 
contractions, per hour. When movement had definitely ceased the specimen was 
considered dead, and opened. The adductor muscle was flabby and soft, instead of 
hard as usual when cut. The heart was not beating but reacted slightly to mechanical 
stimulation. In no other case did death follow so quickly (48 hours) after introduction 
of the liquor. 
It should be pointed out that when a specimen gapes wide open and is unable 
to close it will quickly be eaten whether dead or alive by small crabs and fish. 
Experiments Nos. 16 and 17 ( February 1 to 20, 1980). — Six specimens were 
included in these tests: 2 in each of the liquor solutions, and 2 controls in sea 
water alone. Records were started at 1.10 p. m., February 1. On the 1st, 2d, and 
3d the temperature of the water used varied from 5° to 8° C. after which the water 
was heated and showed a maximum 
variation of from 12° to 18° C., the 
usual range being 14° to 17° C. 
Experiment No. 17 (10 parts 
per thousand). — Water entered the 
mixing chamber at the rate of 90 
cubic centimeters per minute, while 
liquor solution (1 part pure liquor 
to 4 parts sea water) dripped in at 
the rate of 4.6 cubic centimeters per 
minute, producing a solution of 
close to 10 parts per thousand. 
The pH of the solution in the ex- 
periment chamber varied between 
4.7 and 5.6. Liquor was started 
dripping into the mixing chamber 
with the water on February 3 at 2.30 p. m. and continued until the end of the exper- 
iment. Figures 8 and 9 show the results of both experimental and control specimens 
in hours per day that they remained open. All four specimens were closed most of 
the time during the first three days. This was probably due to the low temperature 
of the water at this time. 
From February 4 until death occurred on the 18th, experimental specimen 
No. 1 (fig. 8) stayed open an average of only 7.7 hours per day. The specimen died 
after being in the solution for 14 days, during the first eight of which the valves 
remained tightly closed. 
The reaction of specimen No. 2 was decidedly different. It began to gape open 
(loss of muscle tonus) within two days, and activity became constantly less frequent 
until the final movement was made on the 13 th, nine days after starting of the liquor. 
In several other cases this individual difference in the reactions to the liquor was 
observed. Why this should be the case is not clear, but it appears that the specimens 
which remain closed most of the time live longer than those which remain open in 
the liquor solutions. 
During the period following February 3 the two control specimens (fig. 9) stayed 
open for a high percentage of the time. From February 4 to 20 specimen No. 3 
averaged 23.01 hours per day open, while specimen No. 4 averaged 22.7 hours per 
Figure 8.— Graph showing the number of hours per day that each spec- 
imen in experiment No. 17 (lOparts per 1,000) remained open. The in- 
dividual difference is striking and shows the longer life of the specimen 
which remains closed most. Compare with the control specimens 
shown in Figure 9 
