260 NOTES ON OYSTER CULTURE. 



feet of water. Clean salt water is of course admitted constantly. 

 Here they remain till about February ; they are then taken up and 

 the young oysters detached. This is not difficult owing to the layer 

 of soft lime with which the tiles are coated. When detached they 

 are placed in the "hospitals;" these are generally made of tarred 

 wood (fig. 1, PL XXI) ^ and are shallow trays about six inches deep 

 standing on legs about six inches off the ground ; they rest on the 

 bottom of ponds II and III^ singly or in two tiers^ according to the 

 depth of water (three to five feet) in the pond ; in some cases they 

 are allowed to float. Here the young oysters remain for about two 

 months, increasing in bulk and strength, and recovering from any 

 damage which they may have incurred in detachment from the tiles ; 

 at the end of this time they are sowed out on the private banks in the 

 Schelde as ''zaai-goed/' it being found that, though the percentage 

 of loss is here greater, growth is much more rapid and quality better 

 than if they are kept in enclosed ponds. The grounds on which 

 they are placed are occasionally cleaned by dredging without a net. 

 The oysters are considered marketable in the third and fourth year ; 

 they are dredged up* and brought to the sorting houses, and, ac- 

 cording to size, are either replaced on the beds to grow larger, or 

 are laid down in the store pond marked I. This latter is generally 

 floored with tarred planks, an expensive material, but found to be 

 better than either the natural ground, which becomes foul, or than 

 brick, which is too " cold." On little piles driven into the bottom 

 of this store pond run plank gangways, so that ready access may be 

 had to any part and the oysters lying there be removed by a pole- 

 dredge when required for the market ; the water is kept at about 

 four feet in depth. 



In order to collect the maximum amount of available spat, or, in 

 other words, to bring all the spat within reach of the collectors, ex- 

 periments have for several years been conducted under the auspices 

 of the Nederlandsche Dierkundige Vereeniging on the principle of 

 enclosing breeding oysters with the collectors in ponds. At present 

 the experiments cannot be said to have been entirely successful ; 

 spat is thrown off, and a small quantity certainly adheres to the tiles ; 

 but the difficulty of oxygenating the water and supplying food arti- 

 ficially in the one case, and, if water be pumped through the pond, 

 of keeping the spat from passing through the filter in the other, have 

 so far proved too great, t 



* In some cases steam dredges are used, working six dredges simultaneously. 



t Similar experiments carried out in England have in one or two cases been moi*e 

 successful, though not as yet financially so. Prof. Ryder, in the United States, has devised 

 an ingenious apparatus for the purpose, but no account of its working has as yet appeared 

 (Rep. U. S. Fish Coinm., 1885, p. 321). 



