THE OYSTER. 85 



mud is swept up on to the shallows along the shore, 

 and if these are level, much of the sediment settles 

 there. If, however, the flat is covered by groups of 

 oysters, the ebbing tide does not flow off in an even 

 sheet, but is broken up into thousands of small chan- 

 nels, through which the sediment flows down, to be 

 swept out to sea. 



The oyster-bed thus tends to keep itself clean, and 

 for these various reasons it follows that the more 

 firmly established an oyster-bed is, the better is its 

 chance of perpetuation, since the young spat finds 

 more favorable conditions where there are oysters, or 

 at least shells, already, than it finds anywhere else. 



Now, what is the practical importance of this de- 

 scription of a natural bed ? 



It is this : Since a natural bed tends to remain per- 

 manent, because of the presence of oyster shells, the 

 shelling of bottoms where there are no oysters fur- 

 nishes us with a means for establishing new beds or 

 for increasing the area of the old ones. 



The oyster dredgers state, with perfect truth, that 

 by breaking up the crowded clusters of oysters and 

 by scattering the shells, the use of the dredge tends 

 to enlarge the oyster-beds. The sketch which we have 

 just given shows the truth of this claim, but this is a 

 very rough and crude way of accomplishing this end, 

 and I shall now give a description of the means which 

 have been employed in different places to accom- 

 plish the same result more efficiently and methodi- 

 cally. 



Within recent years, much attention has been given 

 to the possibility of increasing the supply of oysters 

 by artificial means. 



