144 BULLETIN OF THE BUREAU OF FISHERIES. 



Another analogy to the selective power of the blood cells in green-gilled oysters is the 

 selection by certain secreting organs in other animals. Palmer and Eccles have shown 

 that cows fed on carotin will eliminate the pigment through the milk. More than that, 

 they have proven that the carotin will be selected by fat cells and in this form will be 

 received into the milk. 



The kidney cells in all mammals also have a selecting power in separating out 

 certain urine pigments which are later eliminated in the urine. The secretion cells 

 in the oyster doubtless manufacture mucin under ordinary conditions, and probably 

 in the exercise of this function dispose of the green pigment if the oyster again 

 becomes colorless. 



In a continuance of the microscopic study of the greengill, smears were made of 

 the teased tissue of the pigmented gills. These showed the presence of the pigment 

 in large irregularly shaped cells, the granular cytoplasm being distinctly green. These 

 cells moved about in a typical amoeboid manner, which led to the conclusion that 

 possibly the secretion cells were nothing more than leucocytes. Smears of this gill 

 tissue were compared with smears of white gills, and in each case the characteristic 

 amoeboid leucocytes appeared. Wright's bloodstain was then used on several smears, 

 and in each case the green leucocytes stood out green against those of the white gill, 

 which stained red with the eosin of the stain. 



To prove that the Navicula ostrearia was the actual cause of the greening, an 

 attempt was made to develop greengill in a normal white oyster taken from Narra- 

 gansett Bay, where the greengill has never been known. The oyster was placed in 

 aerated sea water which contained the Navicula ostrearia. After a week's time the 

 oyster was examined and showed a pale green color in its gill tissue. To further prove 

 that deposits of green pigment had occurred, smears were made of the gill tissue, and 

 in each case they showed the characteristic green amoeboid cells. Experiments to 

 substantiate this study would have been continued, but the water samples subsequently 

 obtained from Virginia were never very rich in diatom growth, and such efforts on the 

 water samples received seemed futile. A control, however, was run on this greening 

 experiment by placing an oyster from Narragansett Bay into aerated sea water from 

 Virginia which contained no Navicula ostrearia. After a week's time this oyster was 

 examined and showed no green coloration whatsoever. The secretion cells examined 

 in a smear of the gills were normal in appearance. 



The fact that green-gilled oysters depended on the presence of blue diatoms in 

 considerable quantity, and the fact that the water samples from Virginia contained 

 very few of the desired Navicula with which to carry on greening under controlled 

 conditions, suggested the possibility of growing the Navicula in artificial culture media. 

 Efforts, however, were all with negative results. Several culture media were tried at 

 different temperatures, but none seemed to help in cultivating the organism. The 

 solutions tried as media for the artificial cultivation of the diatoms were as follows: 



1. Unfiltered sea water, sp. g. 1.014. 



2. Filtered sea water, sp. g. 1.014. 



3. Filtered sea water, sp. g. 1.014, i per cent lactose brotli. 



4. Filtered sea water, sp. g. 1.014, i per cent dextrose broth. 



5. Filtered sea water, sp. g. 1.014, i per cent oyster broth. 



6. Filtered sea water, sp. g. 1.014, 1 per cent ammonium nitrate. 



7. Filtered sea water, sp. g. 1.014, i per cent ammonium chloride and sodium phosphate. 



8. Filtered sea water, sp. g. 1.014, i per cent urea. 



