82 PROFESSOR RAY LANKESTER. 
able as a coincidence that of late years it should have been 
established that copper in minute quantities is a normal con- 
stituent of the blood of Molluscs. 
Perhaps the strongest argument against the theory that the 
natural green colour of the Marennes is due to copper is (at 
any rate for those who do not place reliance on the results of 
chemical analysis) that the amount of copper sufficient to pro- 
duce the deep colour seen in such an Oyster as that figured in 
Plate VII, fig. 10, would be so large that one dozen (not to 
speak of a few score) of such Oysters must infallibly cause 
severe symptoms of copper-poisoning in one who should swallow 
them. Now, though persons are sometimes afflicted with colic 
after eating a dozen “huitres de Marennes,” the same thing has 
happened after eating a poached egg ; and the experience of man- 
kind is in favour of the opinion that, under normal conditions, 
the “ huitres de Marennes” are as harmless as poached eggs. 
The statements of Professor Bizio with regard to the 
presence of copper being connected with the green coloration 
of the gills of the “ huitres de Marennes,” deserve a little 
further notice. Professor Bizio has the credit of having first 
demonstrated (1835) by chemical analysis the presence of 
minute quantities of copper in the bodies of Mollusca of 
different genera. ‘Ten years later it occurred to him that the 
celebrated French green Oysters might owe their colour to the 
copper which he had discovered in the ordinary brownish- 
grey Oysters of the Venetian lagoons. Professor Bizio 
never examined, and probably never saw, a true “huitre de 
Marennes.” The whole of his essay on the subject in the 
‘Transactions of the Institute of Venice,’ 1845, is in the 
highest degree imaginative. He found that the gills of a 
common colourless Oyster, when allowed to decompose in a glass 
vessel, assumed what he calls an “azure” tint. We have no 
measure or indication of the intensity of this azure, and we 
know further that Bizio, never having seen a “huitre de 
Marennes,” was not in a position to assert, as he did assert, 
that this so-called “azure” colour acquired by a putrefying 
Venetian Oyster was the same thing as the rich blue green of 
