414 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



of them were tinged with an unusual depth of color, so much so that 

 to one unacquainted with the cause they woukl doubless have been re- 

 pulsive, and unlikely to have sfimulated any gustatory feelings. In one 

 of these I found a large cyst or sack near the edge of the mantle, 

 and forming a cavity in its substance one-half inch in length by one- 

 fourth in width. The hearts of the affected specimens were found to 

 have their walls apparently thicker than those of unaffected ones, the 

 muscular trabeculte which interlaced on the inside were found to have 

 entrapped and held in their meshes vast numbers of the loose, green 

 cells precisely like those which freely escaped from the cyst alluded to 

 above. These green cells were quite as independent of each other as 

 the ordinary discoidal corpuscles in the serum of the red blood of a ver- 

 tebrate. The green cells were sometimes confined to the anterior or the 

 posterior wall of the ventricle, sometimes to its upper or its lower end, 

 sometimes the entire ventricle was so loaded with them as to render it 

 quite opaque when viewed with transmitted light. These cells under 

 high powers were invariably found to have about the same appear- 

 ance; were of about the same size, with a distinct nucleus placed eccen- 

 trically; frequently with evidence of pseudopodal prolongations extend- 

 ing laterally from the sides. The nucleus could be very nicely demon- 

 strated with iodine or acetic acid as a refriugent, globular body one 

 six-thousandth of an inch in diameter. The dimensions of the cells 

 would average about one two-thousandth of an inch, or one-fourth of 

 the size of the connective tissue cells. Kow for their identification, 

 which was accomplished as follows : An application of the well-known 

 crucial test for starch gave a negative result. When iodine was first 

 applied to the cells in strong solution, and afterwards treated with snl- 

 phuric acid, with the result that the characteristic blue reaction was not 

 developed, showed that there was ho cellulose wall covering them, and 

 that they were not parasitic algous vegetable organisms. In potassic 

 hydrate they underwent complete solution, a further jjroof of the absence 

 of cellulose and their non-vegetable character. Their dimensions, one 

 two-thousandth of an inch, is about that of the blood-cell of the oyster. 

 The nucleus is in the same i^osition as in the blood-cell of the animal. 

 Their usual occurrence in the gills and frequent presence in the heart, 

 caught in the meshes of the muscular trabeculae of its wall, is almost 

 positive proof of their true origin and character. Furthermore, I find 

 in sections that they sometimes occlude the blood-channels, or are ad- 

 herent to their walls. In the cyst in the mantle, as in the heart, they 

 are free, and in the normal un tinged 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 became green is not 

 easy to determine without a careful examination of some of the local- 

 ities where such green oysters are plentiful. The fact that I found in- 

 stances in green oysters where a greenish material was found in the 

 follicles of the liver, the lining cells of which were also affected, would 



