240 The Histology and Bacteriology of the Oyster. 



tions on Marennes oysters ; but we regard the wandering amoeboid 

 granular cells on the surface of the gills as leucocytes which have 

 escaped from the blood spaces, and have probably assumed a phago- 

 cytic function. 



5. We see no reason to think that any iron which may be asso- 

 ciated with the marennin* in the gills, &c., is taken in through the 

 surface epithelium of the gill 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. 



6. 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, palp, &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 con- 

 nection between the green colour of the " Huitres de Marennes " and 

 the iron they may contain. 



7. 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 those green 

 American oysters than in the colourless ; but this excess is, propor- 

 tionately, considerably less than that of the copper. 



8. 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 Fal- 

 mouth 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 

 oyster. 



9. By treating sections of diseased American oysters under the 

 microscope with potassium ferrocyanide and various other reagents, we 

 find that the copper reactions correspond in distribution with the green 

 coloration ; and we find, moreover, from these micro-chemical observa- 

 tions that the copper is situated in the blood-cells or leucocytes, which 

 are greatly increased in number. This condition may be described as a 

 green leucocytosis, in which copper in notable amount is stored up in 

 the leucocytes. 



10. We find that an aqueous solution of pure hsematoxylin is an 

 extremely delicate test for copper, just as Macallum found it to be for 

 iron. 



1 1 . Experiments in feeding oysters with weak solutions of various 

 copper and iron salts gave no definite results, certainly no clear 

 evidence of any absorption of the metals accompanied by " greening." 



