BULLETIN OF THE UNITED STATES FISH COMMISSION. 413 



kiudly made some delicate tests for me, using small dried fragments of 

 ail oyster very deeply tinged with green in various regions, especially 

 in the liver, connective tissue, and mantl*e. The fragments were burned 

 in a bead of microcosmic salt and chloride of sodium on a clean platinum 

 wire in a gas flame. This test did not give the characteristic sky-blue 

 flame which should have been developed had there been the minutest 

 trace of copper present. This portion of the research I since find was 

 superfluous, as Professor Endlich, of the Smithsonian Institution, in 

 1879, had already gone over the same ground chemically, making every 

 test he could think of to learn whether there was any metallic or other 

 poisonous substance present in some green oysters which had been sub- 

 mitted to him by the health olScers of Washington, who supposed that 

 they might contain something unhealthful, and should therefore be ex- 

 cluded from the market. Professor Endlich, however, found nothing 

 that he considered hurtful. 



Sachs, in his Text-book of Botany, p. 222, says: " The diatoms are the 

 only algse, except the ConjugatiE, in which the chlorophyl occurs in the 

 form of discs and bands, but in some forms it is also found in grains, 

 and the green coloring matter is concealed, like the chlorophyl grains 

 in Fucacese, by a buli-colored substance, diatomine or phycoxanthine." 



It apjiears, then, according to the foregoing quotation, that it is not 

 impossible for diatoms to be the cause of the green color in oysters, and 

 that the objections urged by some against them as a cause of it is founded 

 on a misapprehension of their structure. I find that the liver is normally 

 of a brownish-red color in both the American and. European oysters, 

 but that it often has a decidedly greenish cast in green ones, and that 

 this is due not to a i^arasitic animal or plant, but to a tinction or stain 

 which has affected the internal ends of the cells which line the follicles 

 or ultimate saccules of the liver. This color is able to survive prolonged 

 immersion in chromic acid and alcohol, and does not allow carmine to 

 replace it in sections which have been stained with that color, the effect 

 of which is to produce a result similar to double staining in green and 

 red. The singular green elements scattered through the connective 

 tissue remain equally well defined, and do uot take the carmine dye. I 

 at first believed the green cells to be parasitic. I also supposed that 

 starch granules were apparent, but physical tests failed definitively to 

 ^ reveal them. The large and small green granular bodies in the connect, 

 ive tissue and those close to the intestinal wall I find present in white- 

 fleshed oysters, but simply with this difference, that tkey are devoid of 

 the green color. It is therefore evident from this simple fact that they 

 cannot be of the nature of parasites, though the color is priraarilj^ limited 

 to them only. This condition observed by me in various specimens of 

 American and European oysters does not, however, disprove the possi- 

 bility of the occurrence of vegetable parasites in these animals. 



In some very " poor " Falmouth oysters very much affected with green 

 coloration the gills, heart, and mantle were most notably colored. Some 



