INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 473 



but most of it seems to be done ia May, June, and July. The young, 

 after swimming about for a short time, attach themselves to any suitable 

 hard object, such as rocks, shells, timber, brushy &c. On our coast very 

 few attempts have been made to raise the young oysters by artificial 

 means, because the young oysters, of a size suitable to plant, can gen- 

 erally be bought at a price less than the actual cost of raising them. 

 The time will doubtless come, however, when this will no longer be the 

 case, and then the metnods so successfully employed on the coast of 

 France may be resorted to with great advantage. 



The young oysters must find some solid substance to which they can 

 attach themselves, before losing their locomotive organs, otherwise they 

 will fall to the bottom and perish in the mud. It is evident, therefore, 

 that although the oysters planted on muddy bottoms of the right kind 

 will grow most rapidly, owing to the great abundance of their micro- 

 scopic food in the mud and turbid water j yet such localities are unfa- 

 vorable for breeding-grounds, because the young,or '' spat," will find no 

 suitable objects to which they can attach themselves,unlesSj by chance, 

 to the shells of the old oysters. Therefore, if it be desired to have the 

 oysters in such localities iiroduce the young ones necessary to maintain 

 the bed permanently, it will be necessary to place hard objects on the 

 bottom, to which they may adhere. Stones, broken bricks, «S:c., may be 

 used for this purpose, but nothing is better than old oyster- shells, and 

 they are generally cheaper than anything else. 



On the coast of France bundles of twigs or fagots, prepared tiles, 

 and other objects have been used to catch the young, and the^^ are al- 

 lowed to remain on suxih objects until they become large enough to be 

 removed and planted elsewhere. 



It is obvious that the best breeding-grounds are on hard bottoms, 

 where there are large quantities of dead shells, pebbles, &c., to which 

 the young will be sure to adhere. But such bottoms are not the best 

 localities for the rapid growth and fattening of the oysters. Therefore 

 it is always found profitable to transplant the young oysters, when large 

 enough, from hard bottoms to the muddy bottoms of the estuaries, where 

 their natural food most abounds. 



All muddy bottoms are not equally adapted for this purpose. The great 

 differences to be found in the muddy bottoms of various localities have 

 already been mentioned on a previous page. (Seep. 430.) Those bottoms 

 that are composed mainly of tenacious clay are unsuitable, both because 

 the oysters become imbedded too deeply in the clay, and because such 

 mud contains but little organic matter. Those that consist of clay or 

 sand mixed with decaying vegetable matter, and have a black, x)utrid 

 layer just beneath the surface are also unsuitable and should be avoided. 

 Those that consist of very deep, soft, pasty mud, though the mud itself 

 may be of good quality, are apt to allow the oysters to sink too deeply 

 beneath the surface and thus become smothered in the mud. 



The most suitable localities are those sheltered places where there is 

 a firm substratum of sand or gravel, overlaid with a few inches of soft, 



