SUPPLEMENT. 12 I I 



THEORY OF FATTENING. 



It has long been known that in order to fatten oysters 

 properly, they should be laid down in brackish water, and 

 many estuaries of rivers have long been famous as localities 

 for high-class oysters. Recently the microscope has shown 

 us that it is not the specific gravity of the water that is 

 essential, but the presence of diatomaceae and infusoria, 

 upon which the oyster lives and thrives. On the Whitstable 

 grounds there is, more or less, according to the tides, an 

 eddy over the spot where oysters are laid, and into this 

 eddy are drifted the minute creatures on which the oyster 

 feeds. 



A study of the differently situated oyster grounds will 

 show that there are well-marked differences in the character 

 of the oyster, according to the quantity and quality of the 

 plants and animals which form its food. 



The soil itself has great influence on oyster life, as it 

 affects the production of the organisms which at the various 

 stages of growth are best adapted to the constitution of 

 oysters. 



The green colour of the Essex and Marennes oysters 

 is due to living on a kind of navicula; the green chlorophyll 

 is digested and decomposed ; the soluble colouring matter 

 passes into the circulation of the animal, and. the branchiae, 

 being the most vesicular portions of its structure, are the 

 most highly coloured. Experiments made by MM. Puy- 

 segur and Decaisne proved that if, after oysters had turned 

 green, they were laid in ordinary sea water for a few days, 

 their greenness disappeared altogether. 



The Essex oysters, from the Roach and Crouch rivers, 

 are only green when there is an " r" in the month, that is 

 from September to April, during which time the weed, or 



