• COLORS or DIFPEEENT PARTS OF THE OYSTER. 741 



oyster-crab being perhaps the only creature which is ever frequently found within its valves, 

 and then only as a harmless messmate. More recently it has been my good fortune to be able to 

 study a second lot 'of European Oysters, in two vaileties of which the green color was unusually 

 developed, especially in the heart. In a specimen of Falmouth Oyster I found a large cyst or 

 sac in- the mantle near the edge filled with green cells, which, like those in the heart, when opened 

 readily separated from one another, being quite as i:' dependent of each other as the ordinary 

 discoidal corpuscles in the serum of red blood. The hearts of affected specimens were found to 

 have the wall of the ventricle abnormally thick, and covered inside with the readily detachable 

 green cells in a thick layer and measuring one three-thousandth of an inch in diameter. An appli- 

 cation of the test for starch with iodine gave a negative result. If iodine was first applied to 

 these cells in strong solution, and they were then treated with sulphuric acid, the characteristic 

 blue reaction was not developed, showing that there was no cellulose wall covering them, and 

 that they were most positively not parasitic, algous vegetable organisms. In potassic hydrate 

 solution they were completely dissolved, a further proof of the absence of cellulose. 



Their dimensions, one three- thousandth of an inch, is the same as that of the blood-cell of the 

 Oyster. They are nucleated, with the nucleus in an eccentric position as in the blqod-cell of the 

 animal. Their occurrence in the heart and gills so as to tinge those organs of their own color is 

 almost positive proof of their true origin and character. Furthermore, I find in sections that they 

 sometimes occlude the blood-channels. In the cysts in the mantle, as in the heart, they are free, 

 and in the normal untinged heart they are not abundant. All of the foregoing facts indicate that 

 these green bodies are in reality blood-cells which belong to the animal. How they become green 

 is not CHsy to determine. ,The fact remains that no evidence of the presence of green Micrococci 

 or Microtia, as independent existences, could be made out. The fact that I found instances in green 

 Oysters where an unusual igreenish material was found in the follicles of the liver, the living cells 

 of which were also affected, would indicate that the color was probably absorbed from the food of 

 the animal, which, as we know, consists largely of living vegetable matter. It is not impi-obable 

 that the tinged nutritive juices transuded through the walls of the alimentary canal acquired the 

 color of the food which had been dissolved by the digestive juices. 



How to account for the accumulation of the green cells in the heart and in cysts in thje 

 mantle is not, however, an easy matter, unless one be permitted to suppose that the acquisition 

 of the green color by the blood-cells is in reality a more or less decidedly diseased condition, for 

 which we have no ground in fact, since the green Oysters are in apparently as good health as the 

 white ones. They were found 'fat' or 'poor,' just as it may have happened that their food was 

 abundant or the reverse. They are also found in all stages of the ' greened' condition. Sometimes 

 they have only a very faint tinge of the gills, or they may be so deeply tinged as to appear 

 unpalatable, with the heart of a deep green, or with green cysts developed in the mantle, or with 

 clouds of this color shading the latter organ in certain places. A vastly greater proportion of 

 green Oysters are eaten in this country, at all events, than is generally supposed, especially of 

 those just faintly tinged in the gills. , 



The most important glandular appendage of the alimentary tract of the Oyster is the liver. 

 It communicates by means of a number of wide ducts with a very irregularly formed cavity, which 

 we may designate as the stomach proper, in which the food of the animal comes into contact with 

 the digestive juices poured out by the ultimate follicles of the liver, to undergo solution preparatory 

 to its absorption during its passage through the singularly formed intestine. 



If thin slices of the animal are examined under the microscope we find the walls of the 

 stomach continuous with the walls of the great ducts of the liver. These great ducts divide and. 



