658 OYSTERS, AND ALL ABOUT THEM. 



necessary, then, in order to increase the size of these beds 

 is to render the sea bottom between them habitable for 

 oysters. Old beds increase naturally in size whenever the 

 the shifting and slimy sea bottom which borders them be- 

 comes changed into stable and clear ground. This can 

 take place if changes occur in the force and direction of the 

 ebb and flood currents. In such cases the extension can 

 be hastened artificially by placing upon the newly forming, 

 ground shells of oysters and other molluscs, in order to 

 furnish just outside the borders of the old bed the most 

 judicious objects of attachment for the young broods as 

 they swarm out from the mother oysters. 



For the establishment of new beds, within the limits of 

 the German sea-flats, in places where no oysters are found 

 at present, it will be necessary to find stretches of sea-bottom 

 which are free from mud, where the soil is not being con- 

 stantly shifted about by currents, and where the ebb-tide 

 will leave at least one or two meters in depth of water over 

 the beds. But nearly all such places are occupied by 

 oyster-beds. 



. . . . Over the entire German sea-flats lying 

 south and south-west of Schleswig there can hardly be 

 found a single place which is suitable for the formation of 

 a profitable oyster-bed ; for in front of the mouths of the 

 Eider, Elbe, Weser, Jahde, and Ems the sea-bottom is so 

 covered with mud, or so subject to change, that oysters 

 could not live and multiply there. 



. Whoever, therefore, would establish new 

 oyster-beds along the German portion of the coast of the 

 North Sea, between the Eider and the mouth of the Ems, 

 must begin his difficult work by changing the ebb and 

 flood currents in the southern portion of the North Sea, in 



