294 NATURAL SCIENCE [November 



oyster under normal and abnormal environment, including the effect 

 of sewage matters and pathogenic organisms, drawn up by Professor 

 Herdman, Professor Boyce, and Dr Kohn, are, we think, of sufficient 

 interest to the public to repeat here in full. 



1. There are several distinct kinds of greenness in oysters. 

 Some of these, such as the green Marennes oysters and those of 

 some rivers on the Essex coast, are healthy ; while others, such as 

 some Falmouth oysters containing copper and some American 

 oysters re-bedded on our coast and which have the pale-green 

 leucocytosis we described in the last report, are not in a healthy 

 state. 



2. Some forms of greenness (e.g., the leucocytosis) are certainly 

 associated with the presence of a greatly-increased amount of copper 

 in the oyster, while other forms of greenness (e.g., the Marennes) 

 have no connection with copper, but depend upon the presence of a 

 special pigment Marennin, which may contain a certain amount of 

 iron. 



3. We see no reason to think that the iron in the latter case is 

 taken in through the surface epithelium of the gills and palps ; but 

 regard it, like the rest of the iron in the body, as a product of 

 ordinary digestion and absorption in the alimentary canal and 

 liver. 



4. We do not find that there is any excessive amount of iron 

 in the green Marennes oyster compared with the colourless oyster ; 

 nor do the green parts (gills, palps, &c.) of the Marennes oyster 

 contain either absolutely or relatively to the colourless parts (mantle, 

 &c.) more iron than colourless oysters. We therefore conclude that 

 there is no connection between the green colour of the Huitres de 

 Marennes and the iron they may contain. 



5. On the other hand, we do find by quantitative analysis that 

 there is more copper in the green American oyster than in the 

 colourless one ; and more proportionately in the greener parts than 

 in those that are less green. We therefore conclude that their 

 green colour is due to copper. We also find a greater quantity of 

 iron in these green American oysters than in the coloui'less ; but 

 this excess is, proportionately, considerably less than that of the 

 copper. 



G. In the Falmouth oysters containing an excessive amount of 

 copper, we find that much of the copper is certainly mechanically 

 attached to the surface of the body, and is in a form insoluble in 

 water, probably as a basic carbonate. In addition to this, however, 

 the Falmouth oyster may contain a much larger amount of copper 

 in its tissues than does the normal colourless oyster. In these 

 Falmouth oysters the cause of the green colour may be the same as 

 in the green American oysters. 



