360 
BULLETIN OF THE BUREAU OF FISHERIES 
Table 1 . — Daily averages of values of S ( degree of openness of shell ) and F ( relative rate of flow of water ) — 
Continued 
SERIES V 
Date 
Salinity 
(parts per 
mille) 
Number 
of 5-min- 
ute pe- 
riods 
S (aver- 
age) 
F (aver- 
age) 
Mar. 7.. 
27. 35 
61 
3.~67 
7. 81 
Mar. 8... 
27. 35 
61 
3.60 
7. 15 
Mean 
‘122 
3.63 
7 . 48 
Mar. 9_ 
10. 64 
27 
.61 
0 
Mar. 10 .. 
10. 61 
56 
5. 08 
.03 
Mar. 11 
10. 64 
16 
7. 18 
0 
Mean 
'99 
4.30 
.02 
SERIES VI 
Bate 
Salinity 
(parts per 
mille) 
Number 
of 5-min- 
ute pe- 
riods 
S (aver- 
age) 
F (aver- 
age) 
Mar. 13 
27. 39 
54 
5. 46 
1. 26 
Mar. 14 
27. 39 
54 
5. 37 
1. 13 
27. 39 
63 
6. 41 
.68 
Mar. 16 
27. 32 
51 
6. 72 
.65 
Mar. 17. 
27. 32 
18 
8.48 
.65 
Mean 
‘240 
6.18 
.90 
Apr. 3 
28. 31 
9 
5. 36 
7. 51 
Apr. 11 
20. 90 
70 
5. 80 
5. 05 
28.31 
19 
5. 91 
7. 97 
20. 90 
23 
5. 88 
7. 07 
Apr. 5 
28. 31 
54 
4. 55 
4.91 
Apr. 13 
20. 90 
27 
5. 41 
5. 84 
28. 31 
64 
4. 96 
6. 82 
‘120 
6.72 
6.62 
‘146 
23. 57 
44 
5. 25 
2. 49 
16.31 
72 
4. 49 
1. 15 
Apr. 8 
23. 57 
25 
6. 69 
6. 39 
Apr. 17..- 
16.31 
52 
5. 26 
1.08 
Apr. 10 
23. 57 
43 
4. 75 
2. 74 
Apr. 18. 
16.31 
72 
4. 19 
1. 19 
16.31 
27 
3.94 
.67 
‘112 
S. 46 
‘240 
4.68 
1.07 
SERIES VII 
Nov. 24 
25.09 
94 
2. 37 
2.80 
Nov. 25 
25.09 
15 
3.54 
5. 06 
Nov. 27 
25. 09 
67 
4.52 
6. 57 
Nov. 28 
25. 09 
43 
4. 24 
4. 97 
Nov. 29 
25.09 
55 
5. 06 
6. 54 
Deo. 1 
25. 09 
55 
4.21 
5. 90 
Dec. 2 
25. 09 
55 
4. 70 
4. 70 
Mean 
‘384 
3.98 
6.04 
Dec. 4 
13. 00 
80 
1. 18 
0 
Dec. 5 
13. 00 
31 
5. 71 
2.27 
Dec. 6 
12.98 
81 
3. 90 
.68 
Dec. 7 
12. 98 
32 
4.04 
.71 
Dec. 8 
12. 98 
73 
3. 40 
Dec. 9 
12. 93 
52 
4. 49 
.39 
Dec. 10 
12. 93 
11 
3.81 
.05 
Dec. 11 
12. 93 
80 
3. 18 
.24 
Mean. 
‘440 
S.S9 
.42 
Dec. 12 
25. 53 
88 
2. 73 
2. 51 
Dec. 13 
25.53 
65 
4. 80 
6. 95 
Mean 
‘153 
3.61 
4.40 
‘Total. 
DISCUSSION 
Organisms such as oysters which live in inshore waters, bays, and estuaries are 
necessarily subject to frequent changes in the density or salinity of the medium. 
The observations of Prytherch (1934) indicate that considerable dilution of sea water 
with inflowing fresh water containing copper ions is necessary for the successful 
propagation of the oyster. He also noted that a salinity of from 16 to 18.6 parts per 
mille is optimum for rate of setting, or attachment, of larvae of 0. virginica. The 
natural habitat is thus limited by the salinity of the water, although it may not be 
assumed that diluted sea water is more favorable for growth and feeding after setting 
and metamorphosis have taken place. Most frequently, on the other hand, is it to 
be observed that those grounds which are especially favorable for catching seeds 
are relatively unsuited for the growing and fattening of oysters for market. 
A difficulty of analysis encountered in this work is that even under uniform 
conditions of temperature and salinity there are marked variations in both rate of 
activity of the gills and degree of openness of the valves. Such variability is prob- 
ably to be expected in any study of the reactions of an organism as a whole, for 
