EFFECT OF CRUDE OIL POLLUTION ON OYSTERS 
181 
specific gravity of 0.0002, half that of experiment 122, showed a decrease in rate of 
flow of 33.4 percent, almost exactly the same as no. 122. Finally, oyster no. 178 
(fig. 6), treated for 18 hours with soluble fraction having an increase in specific gravity 
of less than 0.0002, had the rate of flow reduced 78.1 percent, a figure of the same 
order of magnitude obtained in experiment 123. 
Fluctuations in temperature are not significant insofar as their effect on the rate of 
flow is concerned. Experiments 122 and 123, as mentioned above, were carried on 
simultaneously. The temperatures differ little in the two experiments, but the effect 
of the soluble fraction is not at all comparable in amount. It might appear that the 
temperature drop of nearly 5° C. in experiment 178 is partially responsible for the 
relatively large decrease in rate of flow. Actually, this is not the case as can be seen 
by examining figure 6 which presents a complete record of the experiment. 
Six experiments were made with 40 percent soluble fraction, from July 12 to 
August 13. The average temperature of the water in these experiments was 27.2° C. 
Specific gravities of the laboratory sea water were very high, with little fluctuation, the 
range being from 1.0272 to 1.0277 (17.5° C.). 
Except in experiment 142 (table 11), in which the decrease in rate of flow during 
treatment was almost the smallest in the group, the difference in specific gravity 
between the sea water and the soluble fraction was kept within 0.0002. The greatest 
increase in specific gravity of the sea water due to washing (0.0006) occurred in experi- 
ment 153, which was least affected by treatment. The maximum reduction in rate of 
flow following treatment was found in experiment 166, and the soluble fraction used 
here was a mixture from two oils which had been washed 10 and 24 times respectively. 
Five experiments were made with 50 percent soluble fraction solution from July 16 
to September 4. The average temperature of the laboratory sea water during this 
period was 27.3° C. The specific gravity of the sea water varied but little in July and 
August, 1.0273 to 1.0277; but in the last experiment on September 4 it had fallen to 
1.0230. 
The average rate of flow during treatment dropped 66.6 percent. There is 
relatively little difference in the effect of 40 and 50 percent soluble fraction. The 
experiments in the two groups have been separated chiefly to emphasize the close 
agreement between them. 
The main interest of the experiments with 50 percent soluble fraction is the lack 
of any definite relationship between the effect of the soluble fraction and specific 
gravity (table 11, fig. 7). The reduction in rate of flow was practically the same in 
experiment 152, with the high specific gravity of 1.0277, and in experiment 183, with 
the low specific gravity of 1.0230. 
Six experiments were made with 80 percent soluble fraction solution from July 26 
to September 6. The average temperature of the laboratory sea water during this 
time was 27.0° C. Five of the experiments were carried on during July and August, 
when the specific gravity of the laboratory sea water ranged from 1.0270 to 1.0280. 
At the time of the last experiment on September 6, the specific gravity had fallen to 
1.0238. The maximum difference between the specific gravity of the laboratory sea 
water and the soluble fraction was 0.0003. 
The effect of 80 percent soluble fraction was to reduce the activity of the ciliated 
epithelium 90.8 percent. The drop in pumping activity is 24.2 percent greater than 
was found with 50 percent soluble fraction. 
