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. Itis 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 clazres should continue to the end.” It is thus 
necessary that the oysters for the caives 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 aires 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 growing 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 daire 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 c/azres 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 branchie, upon the labial tentacles and intestinal canal ; 
it is often 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 
