384 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
never think that the deficiency might have been caused by the want of a quantity 
of neighboring oysters sufficient to furnish the spat. Nor is one to blame for not 
preserving his oysters to furnish seed for everybody. French political economy has 
assigned to government the duty of reserving oyster-bearing tracts for the common 
good, and the Government has studied where these might most judiciously be located 
so as to profit all alike. The tracts need not be large and would not be of great 
expense to the State, at any rate as an experiment in a single locality. The grounds 
would practically take care of themselves; their only expense would be that of a 
guardian. 
If an experimental oyster tract in one locality should prove eminently successful 
to neighboring seed-culture, a more general legislative action in different States might 
reasonably follow. The matter would certainly be most heartily seconded by the 
oystermen themselves. 
We should not expect seed to be abundant where oysters are lacking. And our 
industry may, for many years to come, demand nothing more pertinent to its welfare 
than State spawning-grounds near centers of oyster-culture. 
The ivaters of the oyster-grounds of the French coast. — A table of densities for comparison. 
Locality. 
Date. 
Specific 
gravity. 
Temp. 
Specific grav- 
ity reduced 
to 15o c. 
standard. 
Remarks. 
1 
Cancale 
Aug. 6 
I,- 1. 025 -1. 0258 
°F. 
74 
1. 0263-1. 0271 
2 
Roscoff 
11 
1. 0252 
73 
1. 0263 
At marine laboratory. 
3 
Belon 
13 
1. 0235-1. 0252 
75 
1. 0249-1. 0266 
Margins and middle of river. 
4 
Lorient 
15 
1. 022 -1. 0225 
74 
1. 0233-1. 0238 
In rearing parks (M. Charles), 1.024(75°) — 1.0245(75°). 
5 
Auray 
16 
1. 0225-1. 023 
67 
1. 0227-1. 0232 
Margins and middle of river. 
6 
JBreneguy 
1.021 
71 
1. 0218 
In basin of production. 
Trinite 
18 
1. 023 
66 
1. 0230 
g 
Sables d’Olonne. 
23 
1. 024 
68 
1. 0243 
Claires about 1.023-1.0235(74°). 
9 
Marennes 
26 
1.023 
73 
1. 0241 
Of. p. 379. 
10 
La Tremblade . . 
27 
1. 023 -1. 024 
76 
1.0246 
Do. 
11 
Areacbon \ 
r 
O 
1. 0185-1. 0245 
69-78 
1. 0189 
During my visit I had opportunities of taking densi- 
12 
Ossegor 
1. 0245-1. 0255 
64-66 
1. 0242-1. 0255 
ties in many parts of the basin. Lowness in spe- 
cific gravity is surprising, since the idea is very 
general that its saltness is greater than that 
of the Mediterranean. As my densimeter was 
made and tested especially for this work, I feel 
confident of my results. The same instrument 
served for all localities and the densities are rela- 
tively just. The greatest density is naturally 
found in the inlet and main channel. The salt- 
ness in the regions where production is most favor- 
able was 1.019—1.021 (about 72°). The least den- 
sities were found in the -\ . and E. parts of the 
basin, due to influx of anumber of draining streams. 
