176 
BULLETIN OF THE BUREAU OF FISHERIES 
Table 11 . — The effect of water-soluble fraction of Lake Barre oil on the rate of pumping of water by 
the gills of the oyster — Continued 
[Cone method, Beaufort, 1934] 
Average ve- 
locity, current 
Effect 
of treat- 
ment 
(percent) 
Dura- 
tion of 
test in 
hours 
Specific gravity, 
17.5° C. 
Increase 
in spe- 
cific 
gravity 
due to 
washing 
Number 
of times 
oil 
washed 
Tempera- 
ture (° C.) 
Experiment no. 
Date 
Before 
Dur- 
ing 
Labora- 
tory sea 
water 
Soluble 
fraction 
Begin- 
ning 
End 
143 
80 PERCENT SOLUBLE 
FRACTION 
July 26 
Aug. 13 
Aug. 15 
63 
0 
0 
18 
1. 0272 
1.0271 
0. 0004 
13 
27.4 
28.2 
165 
66 
27 
40.9 
24 
1. 0277 
1.0276 
.0003 
10 
27.4 
27.0 
171 
85 
1 
1. 2 
24 
1.0280 
1.0281 
.0002 
19 
28.2 
28.2 
172 
Aug. 16 
Aug. 29 
Sept. 6 
53 
2 
3.8 
18 
1. 0277 
1.0279 
.0001 
26 
28.7 
28.2 
177 
62 
0 
0 
18 
1. 0270 
1. 0267 
.0002 
22 
25.3 
21.6 
185 
115 
n 
9.5 
24 
1. 0238 
1. 0241 
.0003 
24 
25.1 
22.8 
74.0 
6.8 
9.2 
131 
100 PERCENT SOLUBLE 
FRACTION 
July 18 
July 23 
July 25 
July 30 
Aug. 3 
Aug. 8 
Aug. 14 
Sept. 4 
76 
0 
0 
1 
1. 0277 
1.0274 
. 0001 
18 
27.9 
27.8 
136 
61 
0 
0 
1 
1. 0273 
1. 0275 
.0003 
12 
27.8 
28.2 
140 
59 
0 
0 
2 
1. 0272 
1. 0272 
.0000 
20 
27. 1 
27.2 
147 
64 
0 
0 
4 
1. 0275 
1. 0274 
.0006 
6 
27.4 
27. 1 
156 
75 
0 
0 
4 
1. 0275 
1. 0275 
.0000 
7 
27.7 
27.0 
162 
51 
28 
54.9 
2 
1. 0274 
1.0276 
.0002 
23 
27. 1 
25.9 
167 
54 
11 
20.4 
6 
1. 0276 
1.0278 
18 
28.6 
28.0 
181 
95 
23 
24.2 
24 
1.0230 
1.0233 
.0002 
23 
24.5 
25.2 
66.9 
7.8 
12.4 
One of the difficulties encountered in these experiments lies in the seasonal 
fluctuations in the laboratory sea water. In preparing soluble fraction there was 
a slight increase in the specific gravity of water owing to washing with oil. How- 
ever, the solution used in various experiments was not always heavier than the 
laboratory sea water used in the same experiment. This was caused by daily fluctu- 
ations in the salinity and the necessity of preparing soluble fraction solution in ad- 
vance of the experiment. The specific gravity of the laboratory sea water used 
during each experiment and the specific gravity of soluble fraction solution are given 
in separate columns. They correspond to the measurements of velocity of current 
before and after treatment. In making up various concentrations of soluble fraction, 
efforts were made in each experiment to adjust the specific gravity of the solution, 
by diluting it with sea water of high or low salinity, as close as possible to that of 
the laboratory sea water. However, this was not alwaj^s feasible. A complete 
record of several experiments with 20-, 50-, and 100-percent soluble fraction are 
given in figures 6 and 7. The vertical lines in these figures indicate time when 
the laboratory sea water was replaced with soluble fraction of oil. 
The figures of the velocity of the current produced by the gills are the averages 
of 10 or more readings in millimeters per second. They all represent the velocity 
at the axis of the tube. In the case of the controls, there is no acutal distinction 
between the periods marked “Before treatment” and “During treatment.” Separa- 
tion has been made aribitrarily on a time basis. To provide a basis for comparison, 
at least 3 readings were made during a period of 2 or more hours before treatment. 
The change in efficiency of the ciliary motion, designated in table 11 as “Effect of 
treatment”, is expressed by the ratio of the average velocity of the current during 
treatment divided by the average velocity before treatment and multiplied by 100. 
The effect of changes in specific gravity on the activity of gill cilia has not been 
studied. However, there was relatively little change in the salinity of the laboratory 
