[25] THE OYSTER AND OYSTER-CULTURE. 107 
ground of the deeper portions of the sea-flats remain surrounded by 
water whose temperature is 2° C. lower than the freezing point of fresh 
water. tn shallow places which the ebb-tide leaves dry, the frost kills 
all animals which have not the ability to dig their way to such a depth 
in the sand and mud that they will be beyond the influence of frost, and 
where the water remains liquid. ! 
Here only a few kinds of mussels, worms, and crabs possess this 
ability; hence all of those sand and mud banks of the sea-flats which 
are left dry by the ebb-tide are comparative ‘“ barrens,” occupied only 
by very few animals and plants. . ; 
Our investigation, then, has led to the grievous conclusion that prof- 
itable artificial oyster-breeding, according to the French system, is not 
possible along our North Sea coasts. Whoever should attempt to carry 
out this system, despite the unfavorable conditions of our waters and 
climate, would be certain to find that his breeding oysters were more 
costly than many English oyster-breeders have found theirs to be; for 
upon the English coasts the difference between ordinary high tide and 
the tide increased by a storm is much less than upon our sea-flats, the 
lowest water does not occur simultaneously with the coldest winds, as 
along the southeast shore of the North Sea, and the climate there is 
milder than upon our coasts. 
8.—CAN NATURAL OYSTER-BEDS BE ENLARGED, AND CAN 
NEW BEDS BE LAID DOWN, ESPECIALLY ALONG THE 
GERMAN COAST? 
It will thus be seen that the German oyster industry remains depend- 
ent now, as ever, upon the natural oyster-banks of our coast-seas, where 
oysters have lived for thousands of years, and where they exist to-day 
fruitful and well-flavored. And in regard to these beds we have now to 
consider the important questions : 
First. Is it possible to increase their size ? 
Second. Can we still farther increase the surface of our oyster-terri- 
tory by laying down new beds ? 
Fig. 9. 
In the foreground are the sea-flats, with two can-buoys which indicate the course of 
the channel for vessels. In the background are seen the dunes or sand-hills of Hor- 
num, the southern point of the island of Sylt. 
The water in the neighborhood of the banks, and over all the stretches 
between them, has the same character as over the banks themselves. 
All that is necessary, then, in order to increase the size of these beds is 
