ON THE LIFE CONDITIONS OF THE OYSTER. 365 



discredit on Bizio's observation ; but we think it very possible, in the 

 light of our recent experience, that Bizio was dealing with the same 

 copper-bearing green pigment that we have met with. 



From numerous analyses that have been made for us by Dr. C. Kohny 

 it is pretty certain that about 0'006 grain (0-4 mgrme.) of copper is the 

 amount that is normally present in the healthy oyster ; and this copper is 

 usually supposed to be located in the htemocyanin, which, as Fredericq 

 and others have shown, is a constituent of the blood of many crustaceans 

 and molluscs. The amount of copper, however, that we have lately found 

 in green oysters is far in excess of what can be accounted for as due to- 

 the haemocyanin. 



Out of 120 American oysters opened at one time, we picked the six 

 greenest and the six whitest. Dr. Kohn analysed these for us and found 

 that the six green ones contained 3'7 times as much copper as the white. 

 This shows that there is an absolute increase in the amount of copper 

 present in the body, and not merely a redisposition, such as the concen- 

 tration of the copper of the haemocyanin in certain leucocytes. 



Further, Dr. Kohn finds that the greenest parts of an oyster, if 

 snipped out and analysed, contain, in a ratio corresponding to that stated 

 above for whole oysters, more copper than the corresponding parts of a. 

 white oyster. These experiments, and the histological reactions described 

 below, demonstrate the coincidence of the copper distribution with the 

 green colour. 



Seat of the Green Colour. 



It may be well that we should state again the method of occurrence 

 and the histological distribution of the green colouring matter. In the- 

 American oyster [0. virginica) re-bedded on the English coast, a well- 

 marked pale chalky green colouration is fi-equently observed, especially 

 in autumn. This colour, in its appearance and distribution, is unlike 

 that seen in the gills of the Marennes oyster. It may occur in patches, 

 on the mantle, but more frequently it is confined to the vessels and 

 heart ; in some cases, owing to the universal injection of the vessels. 

 the entire oyster has a greenish tinge. Microscopic examination shows, 

 that the green colour is due to leucocytes, which are coarsely granular. 

 The leucocytes are amoeboid and tend to collect in masses. The oysters 

 in which this massing of green leucocytes occurs do not appear to us; 

 as healthy as those which are colourless. They are frequently thin,, 

 with the liver shrunken, but we were unable to find evidence of any 

 parasitic or other irritative cause of the disease, either by staining or 

 cultivation. Examination of considerable numbers of the English native 

 {0. edulis) shows that the green colouration is occasionally encountered 

 in that form, and that it is due to the same cause, but it is by no mean* 

 so frequent as in the American species. 



Investigation of the Pigment. 



The following are our details of the histo-chemical investigation of 

 the pigment. The green pigment is insoluble in boiling alcohol, ether, 

 chloroform, xylol, and other fat solvents ; it is soluble in dilute acids and 

 alkalis. The addition of potassic ferrocyanide to sections containing 

 the green colouring matter, or to the leucocytes themselves, gives a red 

 reaction, indicating the presence of copper ; but the reaction can be 



