804 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [12] 



in inakiug histological preparations; for, as a rule, none of these will 

 be absorbed until the tissue has been killed by some other re agents, or 

 not until the cells have been pricked open, so as to break the continuity 

 of their walls, which are not immediately pervious to coloring agents. 

 The fact also that the green color may be again gradually withdrawn 

 by removing the food which is the cause of the viridity, is equally re- 

 markable, and is likewise not a property of other staining fluids used 

 to tinge dead cells, with the exception of some of the anilines, such as 

 Safranin and Dahlia. Yet in this last case the parallel whi5h has been 

 instituted is again unfair, because the anilines are extracted from dead 

 plasma, whereas the green color is withdrawn from the living plasma 

 of the blood cells. 



It is also evident that whatever the nature of the change may be 

 which is induced by the green-coloring principle in the blood-cells of 

 the oyster, that it does not interfere with the nutrition of the animal, 

 which, according to the universal, concurrent testimony of oysterraen, 

 is almost invariably plump and in good condition when its soft parts 

 have become greenish. This is also proof that the coloring material 

 must be more inert than carmine, and must necessarily not be poison- 

 ous, or else the nutritive processes would be greatly interfered with, 

 especially if the color were of mineral origin. For it is known that 

 certain mineral substances have an extraordinarily high chemical equiv- 

 alency when combined with protoplasm ; some mineral salts, such as 

 those of arsenic, lead, copper, and mercury, will enter into combination 

 with many hundreds of times their own weight of living protoplasm; 

 this circumstance seems to explain why these substances are so poison- 

 ous ; vfhj they produce violent symptoms in the process of elimination, 

 or produce a fixed condition of the plasma and death. 



Sometimes the flesh of oysters has a decidedly yellowish cast, verging 

 to brownish-yellow in certain parts, especially the palps, gills, and 

 edges of the mantle. This I have at times supposed to be due to the 

 consumption of large quantities of the tests of diatoms, which were 

 filled mostly with yellowish-brown endochrome or diatomine. If the 

 peptones or ferments secreted by the gastric glands (the liver) of the 

 oyster merely dissolve this material, I see no reason why, under certain 

 circumstances, a pale brownish-yellow tint might not be assumed by 

 the blood-cells of the animal after having absorbed that substance in 

 the same way that they absorb the bluish-green tint. That the brown- 

 ish endochrome might, in short, be carried in solution into the ves- 

 sels and there imbibed by the blood-cells is very probable. That the 

 siliceous tests of diatoms are quickly emptied of their plasma and endo- 

 chrome after they are swallowed by mollusks is shown by the fact that 

 I have never found a diatom in any part of the alimentary canal of the 

 oyster, except the stomach, from which all the contents had not been 

 removed. 



