180 
BULLETIN OF THE BUREAU OF FISHERIES 
104, the increase in specific gravity caused by washing was 0.0001, and the rate of 
flow during treatment was only 59.3 percent of the normal rate before treatment, while 
in experiment 176, the increase in specific gravity was 0.0007, and the rate of flow 
during treatment was 71.8 percent of the normal. 
The difference in specific gravity between the laboratory sea water and the test 
solution was held within close limits, not exceeding 0.0002 in any experiment in this 
group. The specific gravity of the sea water was high in all experiments, ranging 
from 1.0249 to 1.0280. There is no apparent relationship between a high specific 
gravity and effect of the soluble fraction, for the greatest reduction in rate of flow, 
42.9 percent, occurred in experiment 105, in which the specific gravity was 
considerably lower than in experiment 170, specific gravity 1.0280, the reduction in 
flow during treatment for the latter experiment amounting to only 15.8 percent. 
Fluctuations in temperature may be disregarded as factors influencing the rate 
of flow during the experiments, the maximum difference in temperature at the 
beginning and end of an experiment in the 10 percent group not exceeding 1.0° C. 
The time of treatment in this group varied from 12 to 24 hours. Within these limits 
the duration of treatment does not appear to be a factor in determining the effect. 
Three experiments, 104, 105, and 116, were carried on for 18 hours. The first two 
showed the greatest, the last one next to the least effect for the group. 
Seven experiments were made with 20 percent soluble fraction solution. These 
were well distributed over the period from June 14 to August 29. The average 
temperature of the water in these experiments was 27.1° C. Specific gravities 
ranged from 1.0239 to 1.0277. The average reduction in rate of flow resulting from 
this treatment amounted to 54.4 percent. 
In the experiments with 20 percent solution (figs. 6 and 7) the difference in specific 
gravity between the laboratory sea water and the test solution was not held to as low 
limits in all cases as was done in the experiments with 10 percent solution. The 
maximum difference in specific gravity occurred in experiment 99, where the test 
solution was higher by 0.0012. This increase in specific gravity of the soluble fraction 
solution apparently was not of serious proportions in this case, for the reduction in 
rate of flow during treatment was only 17 percent, the lowest for the group. Con- 
sideration was given to the possibility that the comparatively slight effect of soluble 
fraction in experiment 99 might be due, in part, to the relatively low salinity of the 
laboratory sea water, 1.0239, for the other experiments in this group were made when 
the specific gravity was at or above 1.0270. However, an examination of the control 
and other experiments does not support this contention. While most of our experi- 
ments were made with sea water of higher salinity than is found over many oyster 
beds, nevertheless it may be stated that within the range of specific gravities used the 
effect of the soluble fraction is independent of the salt content of the sea water. 
Increase in specific gravity of the sea water after washing with oil has no bearing 
on the effect of the 20 percent soluble fraction. In experiments 122 and 123 (table 11), 
two oysters were treated with portions of the same soluble fraction for 18 hours. 
The increase in specific gravity following washing with oil was 0.0004. The rate of 
flow of oyster 122 was reduced 34.4 percent during treatment. The reduction in rate 
for oyster 123 was 80.8 percent. Oyster 99 was treated for 20 hours with a different 
sample of soluble fraction having the same increase in specific gravity after washing 
and the reduction in rate of flow was 17 percent, comparable to the effect in experiment 
122. Oyster 163, treated for 24 hours with soluble fraction having an increase in 
