The Histology and Bacteriology of the Oyster. 239 



" Observations upon the Normal and Pathological Histology and 

 Bacteriology of the Oyster." By W. A. HERDMAN, D.Sc., 

 F.K.S., Professor of Zoology in University College, Liverpool, 

 and HUBERT BOYCE, M.B., Professor of Pathology in University 

 College, Liverpool. Keceived December 24, 1898, Bead 

 January 19, 1899. 



(Abstract.) 



This research was commenced three years ago, and has been carried 

 on intermittently in the intervals of other work. 



Preliminary reports on some of our results have been, laid before the 

 British Association at the Ipswich, Liverpool, Toronto, and Bristol 

 meetings, and a short paper on one section of the subject was commu- 

 nicated to the Boyal Society and printed in the 'Proceedings' last 

 year. In the present paper we give a full account, with illustrations, 

 of the detailed evidence upon which our various conclusions are based. 

 The following is a brief statement of the more important results given 

 in the paper : 



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

 unhealthy conditions, in order to [elucidate its supposed connection 

 with infective disease, we found it necessary to study in minute detail 

 the histology of certain parts of the body, especially the gills and 

 mantle lobes, the alimentary canal and liver. We give figures and 

 descriptions of these structures in both normal and abnormal condi- 

 tions. 



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

 of a minute muscle, which we believe to be the modified representa- 

 tive of the protractor pedis muscle of some other molluscs. 



3. A diseased condition we found in certain American oysters very 

 soon brought us into contact with the vexed question of the " green- 

 ing" of oysters, and one of the first results we arrived at was that 

 there are several distinct kinds of greenness in oysters. Some of them, 

 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 " described in our 

 former paper to the Eoyal 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., that of the Marennes 

 oysters) have no connection with copper, but depend upon the presence 

 of a special pigment, "marennin." 



We are able, in the main, to support Eay Lankester in his observa- 



