BIVALVE MOLLUSCA. 395 



by the true amateur ; it is the same with indigenous adult oysters. 

 When they are taken at this stage of their existence the colouring does 

 not succeed with them ; — it is only, so to speak, the false brand used 

 to give a speculative value to the merchandise. It is not enough 

 that the mollusc should have a fine flavour ; it must have the peculiar 

 taste. It is not enough that it has the green hue ; it is necessary 

 that these qualities should pervade it from the earliest age, and that 

 the culture of the claircs should continue to the end." It is thus 

 necessary that the oysters for the claires of Marennes should be 

 selected when from twelve to eighteen months old, that the shells 

 should be well-formed and free from all foreign bodies adhering to 

 the surface. Being thus carefully picked out, the oysters are dis- 

 tributed over the bottom of the claires with a shovel, and afterwards 

 so arranged by the hand that they may not touch each other when 

 they increase in size ; that they 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 gro\ving and ripening. They are objects of continual 

 care and of special manipulation. The spring tides visit the claires 

 charged with mud, which, if deposited in the motionless basins, 

 would act as a 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 tentacles and intestinal canal ; 

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

 differ chemically from all other known pignients 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 



