382 THE OCEAN WOKLD. 



do not embarrass each other by the movements of their valves ; and 

 that nothing should interfere with the regularity of their forms. 

 The young colony reposes under a sheet of water from twelve to 

 eighteen inches deep, which is, as we have said, only renewed at 

 spring tides, which reach the level. Nor are the oysters abandoned 

 to themselves in these privileged beds while they are growing and 

 ripening. They are objects of continual care and of special manipula- 

 tion. The spring tides visit the claires charged with mud, which, if 

 deposited in the motionless basins, would act as a mortal poison to 

 the young mollusc; hence the necessity of transporting them from 

 one claire charged with mud into others free from such accumulations ; 

 and this is a process in constant operation until the animals are finally 

 gathered for consumption. Oysters deposited in the claires aged 

 eighteen months should remain two years before they are ready for 

 use ; but three and even four years are required to give them the full 

 degree of perfection which characterises the best products of the 

 Marennes oyster-parks. 



Oysters placed in the reservoirs in an adult state become green, it is 

 true, in a very few days, but they never attain the exquisite flavour of 

 those which have been bred in the parks, and have undergone the 

 costly manipulation described from their earliest years. 



The question arises, What is the colouring principle which is here 

 in operation ? The green colour is not general ; it is shown princi- 

 pally on the branchiae, upon the labial feelers and intestinal canal ; 

 it is rather undecided ; and the colouring matter appears to differ 

 chemically from all other known pigments of green colour. Must it 

 be attributed to the soil of the claire ? This is its most probable 

 origin. But many naturalists insist that the colouring matter proceeds 

 from an infusorial animalcule, the green-coloured Yibrion. Others 

 have hazarded the opinion that it is a disease of the liver in our 

 unfortunate bivalve which produces the colour. Bile secreted in 

 excess by a diseased liver would give a green hue to the parenchyma 

 of the respiratory organs of an animal rendered sick by the excep- 

 tional treatment to which it has been subjected. Of these three 

 opinions, says M. Figuier, the first, as we have said, presents the 

 greatest appearance of probability. 



The system of oyster farms, which has worked admirably for the 



