214 FISHERIES OF THE UNITED STATES. [30] 



and extension of an oyster-bed are due largely to this ability of the 

 young fry to hold on to anything and everything. The beginning of a 

 bed is probably in most cases accidental. There is an exposure of some 

 object suitable for attachment, to which the drifting embryos cling, and 

 succeeding seasons add to the colony and slowly increase both its pop- 

 ulation and area ; the natural limits are defined by the amount of food 

 and constituents of shell available, the amount of room for develop- 

 ment, and the character of surrounding, contiguous bottoms. Oysters 

 cannot live on bottoms not sufficiently consistent to support them ; 

 they are unprovided with siphons, or means of locomotion, and if sunk 

 in mud or sand will perish. Neither can they live for long periods out 

 of water unless especially educated for that contingency. 



Natural oyster-beds on the American coast are of two classes; worked 

 and unworked beds, each presenting marked features. 



The following extracts from the reports of Mr. Winslow to the Super- 

 intendent of the United States Coast Survey, describing areas in Ches- 

 apeake Bay, indicate the salient features of each class. The beds con- 

 trasted are located in Chesapeake Bay and Tangier Sound, an adjacent 

 estuary of the bay. 



"Generally speaking, here as in the Sounds, the original beds were 

 formed on the side of the shoals, and wherever there was a sudden 

 change of bottom. 



"Whenever the solid beds or 'Bocks' were encountered, they were 

 found to be long and narrow ridges, extending generally in a northerly 

 and southerly direction, except when near Kedge's Strait, where they 

 ran more to the eastward and westward ; and we could, in standing 

 across the beds, but rarely obtain more than one or two hauls of the 

 dredge before we were off the ' Bock.' The major axis appears here, as 

 elsewhere, to lie in the direction of the current, and probably all natural 

 extension and growth of any bed are in that direction, the spat being 

 carried backward and forward by the ebb and flow of the tides. The 

 large number of beds near and off Kedge's Strait is probably due to the 

 large number of spat brought out from the Sounds through the Strait. 



" The bottom is generally of hard sand covered with sponge and grass. 

 Near Kedge's Strait some mud sloughs were found, and in some cases 

 the substratum of the beds was of clay ; but in most of them the stratum 

 of oysters and shells was too thick and hard to be penetrated. 



" The beds outside the Sounds have been comparatively free from 

 dredgiug, and thus present marked differences from those inside. 



" They are comparatively longer and narrower, and much more sharply 

 defined. Very few scattered oysters are found near them, and the beds 

 are much more solid, unbroken, and much harder, requiring heavier 

 dredges than those used in the Sounds. The most remarkable difference 

 is, however, in the shape and growth of the oysters. 



" On the undredged beds they are long and narrow, with the lower 

 shells very deep and bills very thin and sharp. In no case did we find 



