234 Our Food Mollusks 



on beaches and flats in the Chesapeake or Long Island 

 waters, as they do here? All Atlantic oysters are of one 

 species, and in all regions their habits are probably 

 identical; yet in one place they grow and reproduce on 

 periodically exposed flats, and in the other, only on the 

 bottom below tide lines. The answer is that they do at- 

 tach between the tide lines in the northern fields, but that 

 very early in the terrible northern winter, every such un- 

 fortunate perishes from cold. 



But a second question is not so easily answered. Why, 

 in these marginal waters of the Carolina sounds, do 

 oysters not more often appear on the bottoms below the 

 tide lines? Farther north it is only in such a position 

 that they establish themselves. Several suggestions 

 have been made concerning conditions that might ex- 

 plain the phenomenon. The most plausible is that the 

 water is so heavily burdened with silt, frequently depos- 

 ited, that very young oysters are smothered, even when 

 not actually covered by it, possibly, it has been suggested, 

 because their gills become encumbered with mud par- 

 ticles. This probably is not true. The gill of the adult 

 can free itself of any quantity of mud, as may be shown 

 by experiment. Adult oysters sometimes survive when 

 deposits have been so heavy as to cover them to a depth 

 of several inches, the gill currents keeping an opening 

 through the mud like the burrow of a clam. The gills 

 of the young probably are not less capable of keeping 

 their surfaces clean. 



The fall of silt in some waters may, of course, be so 

 heavy as to cover, and thus to smother, recently attached 

 oysters; but even when less heavy, it may, when long 

 continued, lead to their death, not by smothering, or 

 preventing the oxygenation of the blood, but by starv- 



