CONTINENTAL OYSTER CULTURE. 377 



But when it is present, and the site is otherwise eligible, there 

 is still the question of the bottom. The system of culture must 

 either be adapted to this, or a site must be found in which the 

 nature of the bottom is adapted to the system. This is the 

 general rule, but in cases where the Oysters are to be reared in 

 floating ambulances, as at Thau, the nature of the ground is 

 immaterial. 



Except where the bottom is too hard for stake-driving, the 

 Italian Tarantine method can be used anywhere. But the best 

 site is where the bottom is of good holding material ; and where 

 the water is not less than 4 yards nor more than 12 yards deep — 

 a less depth exposes the Oysters to sudden changes of temperature, 

 and a greater depth makes stake-driving difficult and costly. 

 The palisade may in general be rectangular, long and narrow, 

 with the head or short side facing the prevailing wind or 

 current. 



For the French and Dutch systems of bedding, clean firm 

 bottoms, such as coarse sand, gravel, hard clay, are required, and 

 the best arrangement is one that permits the operator at will to 

 draw off the water at low tide, so as to sort and arrange the 

 Oysters at ease, and give them daily exposure to the air. This 

 periodical exposure is an important commercial item, as it is 

 found that Oysters so habituated live for a longer time out of 

 water. 



The Austrian is not a hard and fast system, but inclining 

 mostly to the Italian practice, utilizes also French methods 

 according to the nature of the ground. 



In comparing the relative advantages of the several systems, 

 it appears that Oysters laid to mature on the bottom, as in the 

 French and Dutch methods, are more exposed to the attacks of 

 worms, Crustacea, and molluscs, &c, and, unless daily exposed to 

 the air, they do not acquire the property of remaining many days 

 closed when taken out of water ; lastly, they develop slowly, and 

 do not reach saleable size till after the second or third year, and 

 are not sold as Oysters of first quality till the fourth year. On 

 the other hand, the system is perhaps cheaper, and the Oysters 

 are more regular in shape and stronger in shell. Where Oysters 

 are grown entirely in ambulances, the system shares the advantages 

 of the Italian method, in which the Oysters are suspended and 



ZOOLOGIST, THIRD SERIES, VOL. XVIII. OCT. 1894. 2 G 



