168 TRANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



colour to sesquioxide of iron in the mud of the " claire." 

 This revival of an old view I have alluded to above. 



At present then there are several distinct views as to 

 the exact cause and the meaning of the greenness of the 

 French cultivated oyster which is fattened, flavoured and 

 greened in the oyster parks or " claires " of La Tremblade, 

 Marennes, Sable d'Olonne, Le Croisic and other places 

 on the west coast of France. One view is that it is due 

 to the microscopic food of the oyster, another that it is 

 caused by the nature of the bottom of the " claire." One 

 view is that it is a process of excretion or the removal of 

 certain coloured matters from the body, another that it is 

 a process of absorption of nutriment. The whole subject 

 is at present under investigation both by ourselves and 

 by others, and we hope to report upon our conclusions 

 more fully in a few months. It cannot, however, be 

 questioned that the normal green oyster of the French 

 markets is in a thoroughly healthy condition and that its 

 green colour is not due to copper nor to any other 

 poisonous substance. 



There are, however, other green oysters — or rather 

 there is a greenness which may appear in any oyster 

 under certain conditions — which have nothing to do with 

 cultivation in "claires" and where the colour is not due 

 to feeding upon diatoms. This is the pale greenness 

 mentioned above which we have met with in some 

 American oysters. We find that it is an inflammatory 

 condition or " leucocytosis " in which enormous numbers 

 of wandering leucocytes filled with large green granules 

 come out on the surface of the body and especially on the 

 mantle. For further details of this green condition of 

 the oyster, with figures, I must refer to our full report to 

 the British Association to be published later. We have 

 tried growing oysters under various unusual conditions, 



