On a Green Leucocytosis in Oysters. 



31 



largely due to the fact that the observers worked with different kinds 

 of oysters. Some have investigated the celebrated " Huitres de 

 Marennes" (a form of Ostrea edulis), and have found that while 

 having dark blue-green gills, they were still in a perfectly healthy 

 state, that they contained very little copper, and that some iron was 

 present in the pigment. All that is perfectly correct, but it does 

 not enable us to draw any conclusions in regard to other green 

 oysters. There are evidently several kinds of greenness in oysters, 

 and whereas some may be due to normal and healthy processes, others 

 must be regarded as abnormal or diseased conditions. It is the 

 latter, in our experience, that contain the copper. 



As early as 1835, Bizio showed that certain oysters he obtained at 

 Venice contained copper, and he attributed (1845) their bluish- 

 green colour, and that of the Marennes oyster, to the presence of 

 that metal. Two subsequent discoveries have thrown a certain 

 amount of probably undeserved discredit upon Bizio's work. These 

 are (1) the determination by Fredericq and others that a certain 

 small amount of copper is present normally in the haemocyanin 

 of the blood of crustaceans and molluscs; and (2) the excellent 

 work of Lankester* and others on the Marennes oysters which 

 established the normal, healthy condition of the greenness, and the 

 absence in that form of any copper beyond the trace due to heemo- 

 cyanin. We now think it very probable, in the light of oar recent 

 experience, that Bizio was dealing, in the case of his Venetian 

 oysters, with the same copper-bearing green pigment that we have 

 met with. 



About 1880 Ryder investigated some green oysters in America, 

 and from his description of what he found we cannot doubt that he 

 had before him the same kind of green American oyster (Ostrea 

 virginica) that we have been examining. He showed that the green 

 colouring matter was taken up by the amoeboid blood cells, and that 

 these wandering cells containing the pigment were to be found in 

 the heart, in some of the blood vessels, and in aggregations in 

 " cysts " under the surface epithelium of the body. He describes 

 the colour (in the ventricle) as a " delicate pea-green," and states 

 that it is not chlorophyll nor diatomine : he suggests that it may be 

 phycocyanin or some allied substance. f 



So far as we are aware there has been no work £ since Byder's, 



* See Professor Lankester's memoir on " Green Oysters," in the c Quart. Jour. 

 Micro. Sci.' for 1886, which gives an excellent discussion of the subject so far as 

 the Marennes oyster is concerned. 



t Ryder's papers are in the 'U.S. Fish. Commission Reports and Bulletins' 

 rom 1882 to 1885. 



X Except Carazzi's passing allusions to our work in 1 Mitth. Zool. Stat. INTeapel ' 

 for 1896. His own investigations were made upon other kinds of oysters. 



