[473] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 179 
but most of it seems to be done in 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, brush, &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 methods 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; 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,unless, by chance, 
to the shells of the old oysters. Therefore, if it be desired to have the 
oysters in such localities produce 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, &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 they are al- 
lowed to remain on such 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, &e., 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. (See p. 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, putrid 
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, 
