[39] THE OYSTER AND OYSTER-CULTURE. Won 
These beds are only from 1,000 to 1,050 meters long by about 300 meters 
broad, while the Huntje Bank is more than 1,800 meters long by about 
900 broad. . The speedy extension of oysters in the Lim Fiord has taught 
us that young swarm-oysters can wander from 4 to 8 kilometers away 
from their home-bed before they become attached to any object. So if 
the oyster-bank is of small extent, the young oysters are in danger of 
swimming out beyond the limits of the bed and settling upon unsuitable 
ground, and thus of being destroyed in much larger numbers than upon 
a larger bed. Of such broods of swarm-oysters the large banks will re- 
tain many more than the small beds; and if upon both all other con- 
ditions are the same, a much larger number of young will grow to ma- 
turity upon those beds which have a large extent of surface than upon 
the smaller beds. 
10.—AN OYSTER-BANK IS A BIOCONOSE, OR A SOCIAL COM. 
MUNITY. 
The history of the impoverishment of the French oyster-beds is very 
instructive. When the beds of Cancale had been nearly deprived of 
all their oysters, by reason of excessive fishing, with no protection, the 
cockle (Cardium edule) came in and occupied them in place of the oyster; 
and vast hordes of edible mussels (Mytilus edulis) under similar cireum- 
stances appeared upon the exhausted beds near Rochefort, Marennes, 
and the island of Oléron. The territory of an oyster-bed is not inhabited 
by oysters alone but also by other animals. Over the Schleswig-Hol- 
stein sea-flats, and also along the mouths of English rivers, I have ob- 
served that the oyster-beds are richer in all kinds of animal life than any 
other portion of the sea-bottom. As soon as the oystermen have emptied 
out a full dredge upon the deck of their vessel, one can see nimble pocket- 
crabs (Carcinus menas) and slow horn-crabs (Hyas aranea) begin to work 
their way out of the heap of shells and living oysters, and try to get to 
the water once more. Old abandoned snail-shells begin to move about, 
caused by the hermit-crabs (Pagarus bernhardus), which have taken up 
their residence in them, trying to creep out of the heap with their dwell- 
ing. Spiral-shelled snails (Buccinum undatum) stretch their bodies as 
far out of the shell as they can, and twist from side to side, trying, with 
all their power, to roll themselves once more into the water. Red star- 
fish (Asteracanthion rubens), with five broad arms, lie flat upon the deck, 
not moving from the place, although their hundreds of bottle-shaped 
feet are in constant motion. Sea-urchins (Hchinus miliaris), of the size 
of a small apple, bristling with greenish spines, lie motionless in the 
heap. Here and there a ring-worm (Nereis pelagica), of a changeable 
bluish color, slips out of the mass of partially dead, partially living, ani- 
mals. Black edible mussels (Mytilus edulis) and white cockles (Cardium 
edule) lie there with shells as firmly closed as are those of the oysters. 
Even the shells of the living oysters are inhabited. Barnacles (Balanus 
S. Mis, 29 46 
