148 BULLETIN OF THE BUREAU OF FISHERIES. 



Small pieces of the pigmented gill were placed in sterile water and shaken up 

 thoroughly and then plated out on nutrient agar in Petri dishes, with the usual bacteri- 

 ological technique. No color-producing organisms were obtained in three trials. Abun- 

 dant colonies of white bacteria were observed. 



CONCLUSION. 



The investigations seem to warrant the following conclusions : 



1. The Chesapeake green-gilled oyster is the same as the so-called Marennes oyster." 

 This conclusion is reached since the Virginia oyster corresponds exactly to the descrip- 

 tions of the Marennes oyster in general appearance and in microscopic examination. The 

 greengills and palps of our southern oyster coincide precisely with the descriptions and 

 drawings of the French oysters, and the method of distribution by secretion cells and 

 the location of the pigment in definite tissues of the gills, as explained by Lankester, 

 is the same as has been found in these obsers'^ations of the Lynnhaven oyster. A 

 diatom answering the same description as the Navicula ostrearia, recognized as the cause 

 of the greening of Marennes oysters, has been identified wherever green oysters were found 

 in the Chesapeake. The frustules of the diatom have also been obtained from the 

 intestines of the green oysters in this observation exactly as Lankester noted in his 

 study of the Marennes oyster. Again, this investigation agrees thoroughly with the 

 conclusions of several European workers that the pigmentation of the gill can occur 

 by allowing the oyster to remain in sea water in which there are NavictUa ostrearia, but 

 that there is no coloration if the Navicula are absent. 



The observations in this investigation on the chemistry of the pigment of Chesapeake 

 green oysters are exactly the same as those made on the Marennes greengills by Lankester. 

 The extreme insolubility of the pigment noted by this investigator as characteristic of 

 the European oyster is in direct harmony with the studies recorded in this investigation. 



2. No evidence that the coloration of the gills of Chesapeake green oysters was due 

 to bacteria was found in the investigation. 



3. The pigment found in the greengills of Chesapeake Bay oysters yields a saponifica- 

 tion product that shows an absorption band covering the violet of the spectrum. 



a This statement must be understood as referring to the color and its cause, the only subject treated in this paper, Euro- 

 pean oysters, as is well known, are not of the same species as American oysters. Marennes oysters in Europe are prized 

 above others, because of the excellent qualities associated with the green-gilled condition. This paper shows that the green- 

 gilled condition in American oysters is identical with that in the oysters of Marennes. 



