62 



The discovery of a green tinge of more or less intensity 

 which made its appearance on the mantle and other parts 

 of the body of some of the oysters in our experiments 

 started us on a series of investigations into the minute 

 structure of the green parts, and the nature and causes of 

 the greenness in general in oysters. We soon found that 

 the greenness of our experimental oysters,* which is very 

 different in appearance from the greenness of the culti- 

 vated French oyster — the " huitre de Marennes " — was 

 present also in some American oysters freshly imported, 

 and was liable to make its appearance in oysters laid 

 down in certain parts of our own coast. We found that 

 this pale green mflammation, as it may be called, was 

 known to the local oyster importers and oyster merchants, 

 by whom the suggestion was made that the colour was 

 due to copper poisoning in the oyster. 



This led us to a chemical examination of the matter 

 which showed (as had been shown in the case of other 

 green oysters before) that copper had nothing to do with 

 the disease. There was very little copper present in the 

 green parts — practically no more than in the corresponding 

 parts of colourless (yellow) oysters. Moreover we have 

 kept oysters in old copper vessels and in vessels of sea 

 water containing different amounts of sulphate of copper 

 in solution (0"02 and 0"2 % of the copper, in 10 litres of 

 water), and other salts, and in none of these cases did the 

 animal acquire any green colour except what was deposited 

 on the surface of the shell and other exposed parts until 

 the death of the tissues when a certain amount of post- 

 mortem green staining made its appearance. 



Dr. Charles Kohn has kindly analysed the gills of some 

 green (French) and some ordinary colourless oysters, and 



*Oiir thanks are due to Charles Petrie, Esq,, CO., and to George T. G, 

 Mussonj Esq., for the kind help they have given lis in procuring various 

 kiuds of oysters for investigation and experiment. 



