ARTIFICIAL OYSTER CULTIVATION. 1185 



The oysters are generally from twelve to eighteen 

 months old when placed in these greening claires, and 

 they remain there for two years or so, growing and fatten- 

 ing ; during this time they should be shifted from one 

 pond to another to ensure successful results. Many, how- 

 ever, remain in the ponds a much shorter time, as it is 

 often the practice to place mature oysters in these pares 

 for a few weeks to acquire the green beards, which they do 

 at a comparatively cheap rate, though they do not acquire 

 the flavour of those oysters that have been in the ponds 

 their usual time. 



We have already referred to the cause of the green- 

 finned oysters under the head of Natural History, but in 

 consequence of the groundless prejudice which exists 

 against them in England, and which is the cause of the 

 exportation of all our Essex green beards to Ostend, we 

 think it desirable again to state that this colour is caused 

 solely and entirely by vegetable matter, and is not only 

 quite harmless, but imparts an exquisite flavour to the 

 oyster. 



Oysters and other molluscs undoubtedly do absorb 

 and retain copper in their tissues when placed in solutions 

 containing it ; but in every case that has been looked into, 

 and many experiments have been conducted by competent 

 analysts with reference to this matter, the copper has been 

 found in the body only of the oyster which is coloured 

 bluish- green, and not in the beard which was not green. 

 In green-bearded oysters the body of the fish is of the 

 usual or of a very slightly greenish tint, and has never been 

 found to contain a trace of copper. 



Before leaving this part of our subject, we are tempted 

 to remark that, in theory, oyster culture seems so simple a 

 thing, that the wonder is there are so many failures at it. 



NN 



