(53) 



XIV.— CONCLUSIONS. 



1. Although our primary object was to study the oyster under unhealthy con- 

 ditions, in order to elucidate its supposed connection with infective disease, we found it 

 necessary to investigate in minute detail the histology of certain parts of the body — 

 especially the gills and mantle-lobes, the alimentary canal and the liver. We give 

 figures and descriptions of parts of these structures in both normal and abnormal 

 conditions. 



2. We have also worked out the distribution and probable function of a minute 

 muscle, which we believe to be the modified representative of the protractor pedis 

 muscle of some other Molluscs. 



3. A diseased condition we found in some of our experimental oysters very soon 

 brought us in contact with the vexed question of "greening" in oysters, and one of 

 the first results we arrived at was that 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 a paper to the Royal Society, are not in a healthy 

 state. 



4. 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 possibly be associated with a 

 certain amount of iron. 



5. 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. 



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, 

 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. 



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 these green American 

 oysters than in the colourless ; but this excess is, proportionately, considerably less than 

 that of the copper. 



