724 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [42] 
cial community, even in the great seas. Oyster-beds are formed only 
upon firm ground which is free from mud, and if upon such ground 
the young swarming oysters become attached in great numbers close 
together, as happened upon the artificial receptacles in the Bay of Saint. 
Brieux, their growth is very much impeded, since the shell of one soon 
comes in contact with that of another, and they are thus unable to 
grow with perfect freedom. Not only are they impeded in growth in 
this manner, but each oyster can obtain less nourishment when placed 
close together than when lying far apart. 
In an oyster-breeding trench upon the island of Hayling, in the south 
of England, I saw, in May, 1869, oysters three years old which had grown 
thus far towards maturity attached to hurdles. Nearly all had twisted 
shells, which were not larger in diameter than from 2 to 3 centimeters, 
while a Holstein oyster three years old is from 5 to 6.5 centimeters broad. 
Evidently, thé reason for their small size is to be found in the fact that 
in the trench they receive less nourishment daily than they would in 
the open sea. In the Bay of Arcachon the breeders are obliged to loosen 
the oysters from their artificial points of attachment and place them in 
boxes and trenches where they can grow to maturity, and in these 
the oysters must not be placed too close together or they will not grow 
to the best advantage. Even upon the best beds the oysters will remain 
poor if they are allowed to lie too thick upon the bottom; but if a por- 
tion of these poorly nourished oysters are taken away, those which re- 
main—as has been found out by experience upon the Huntje Bank, the 
largest and most fruitful of all the Schleswig-Holstein beds—will soon 
become fatter, that is, their generative organs will become larger because 
more ege’s or spermatozo a are produced than with poorer oysters. Thus, 
if a bed is above its mean in productiveness, every single one of the ex- 
cessive throng of full and half grown oysters will not receive sufficient 
nourishment to enable them to generate a full number of germs, so that 
the number of germs produced and the number of young which arrive 
at maturity being thus regulated the entire bank will very soon be 
brought back to its former or normal condition. Since this law is in 
operation upon even the most productive of the Schleswig-Holstein beds, 
where the number of young which arrive at maturity is 484 for every 
thousand of mature @ oy sters, while the average for all the beds is only 
421 to each thousand, then a productiveness of 484 to the thousand is 
the highest which can be reached and maintained among the oysters 
existing under the biocénotic conditions of our sea-flats. Near Auray, 
in Brittany, the oyster-breeders collect many more young than they can 
grow to maturity, since they possess comparatively little oyster-terri- 
tory, and this territory is not supplied with sufficient suitable food to 
nourish large numbers of oysters; so that whenever the breeders fail 
to find a purchaser for their extra stock of young they lose all the 
profits of their labor. Thus, it is with oysters as with all other 
animals; their increase in size and numbers depends upon the quantity 
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