OCCURRENCE IN VIRGINIA OF GREEN-GILLED OYSTERS. 1 39 



3. That there is some mechanism in the oyster by which the pigment of the Navicula 

 ostrearia, being taken into the oyster's ahmentary canal, can be absorbed and deposited 

 in the gills and palps. 



These points Lankester well brought out. He concluded, through the fact that he 

 found many f rustules of the diatoms in the intestines and stomachs of green-gilled oysters, 

 that they must have swallowed them. Further than that, he observ^ed the pigment oi 

 the Navicula ostrearia chemically and spectroscopically and found it to have exactly the 

 same properties as the green pigment of the Marennes oyster. L,ankester also did con- 

 siderable work on the histology of the oyster gill in an effort to find and demonstrate 

 the exact distribution of the pigment. This distribution of green material he found to 

 be in amoeboid leucocytes that work their way through the epitheUal cells of the gills 

 and move around on the external surface of the gills. These cells he called "secretion 

 cells," and they are found on all normal oyster gills. With this work Lankester also 

 published a minute description and a set of colored drawings of the Navicula ostrearia 

 and the distribution of its pigment throughout the oyster. 



In 1899 Herdman and Boyce, two Enghsh investigators, published a paper on 

 "Oysters and Disease," in which they drew attention to the fact that copper-green 

 oysters and green-gilled oysters were two different abnormalities. This paper was 

 merely a review of the work that had been done on the green oysters up to that time, 

 supplemented by a study of the histology of the two different types of green abnormality. 

 Ryder, whose work has been published in several United States Fish Commission reports, 

 did much investigation on green oysters, but the copper-green oyster received his atten- 

 tion especially. 



The only papers dealing with the conditions that show the effect environment may 

 have on the growth of the Navicula ostrearia and the consequent greening of the oysters 

 are those by Boub^s and Calvet. Boub^s, in his " L'ostreiculture k Arcachon," gives a 

 general survey of natural, legal, and economic conditions affecting the oyster industry 

 at Arcachon, contrasting these with circumstances at Marennes. In this publication he 

 mentions the most important fact that, when the claires are allowed to get too salt, the 

 product, the greengill, is not so good. He intimates in this statement that a high 

 specific gravity is not conducive to the life of Navicula ostrearia. Calvet, 1910, in 

 "Du Vertissement des Huitres," discusses the conditions that tend toward an optimum 

 "greening" of oysters left in the claires, taking into consideration the temperature, the 

 specific gravity of the water, the depth of the water, the nature of the bottom, and the 

 effect of light on the growth of the Navicula ostrearia, and therewith the greening of 

 the gills. 



THE GREEN-GILLED OYSTERS OF VIRGINIA. 



The oysters found to possess this abnormal condition in Virginia were the large 

 typical Chesapeake oysters. The gills at the height of the epidemic showed a green 

 color, which extended in many cases up into the palps, turning them, also, a greenish 

 color. The liver appeared a somewhat darker brown than in the normal oyster, but 

 the rest of the oyster's body seemed perfectly normal. The larger number of the 

 oysters observed were in a well-nourished condition and appeared very "fat." Indeed, 

 the people in the vicinity of Lynnhaven used them freely, claiming that they possessed 

 a more delicate flavor than the ordinary white oyster. The oyster dealers of the place 

 also shipped considerable quantities to distant destinations where, according to reports, 

 they received ready sale. 



