740 NATURAL HISTORY OF AQUATIC ANIMALS. 



fore, not a part of Hie animal but a distinct vegetable organism. These facts, observed a long- 

 time since, render it very probable that Professor Leidy was one of the first to notice the intra- 

 cellnlar parasitism of a plant in an animal. 



The green color of the Oyster, as far as my experience goes, is not intense, as in many green 

 animals, such as we observe in Stentor, Spongilla, Hydra, etc., but is a pale pea-green tint. This 

 has been found to bo the color of affected natives as well as of foreign ones, the gills and mantle 

 being usually. most distinctly tinged. Exceptionally the heart is affected, its color sometimes 

 being quite intense. 



EXPERIMENTS UPON EUROPEAN OYSTERS. In studying some Oysters which were obtained 

 from England through the kind offices of Messrs. Shaffer and Blackford, in response to a request 

 corniug from Professor Baird, certain ones were found which were decidedly green. Of these the 

 French specimens of Ostrca edulis, and a very singular form, labeled " Anglo-Portuguese," had the 

 gills affected, and in some of the latter the liver, heart, and mantle were very deeply tinged in 

 certain parts, so much so that I decided to make as critical an examination as my resources could 

 command. 



Spectroscopic investigations gave only negative results, as it was found impossible to discern 

 any positive evidence of chlorophyl from the spectrum of light passed through thin preparations 

 made from specimens of green-tinted Oyster, some of whicb, like those made from the heart, are 

 decidedly green to the naked eye. There was no absorption noticed at the red and blue ends of 

 the spectrum, such as is observed when the light which enters the slit of the spectroscope first 

 passes through an alcoholic solution of leaf green or chlorophyl ; indeed, the spectrum did not 

 appear to be sensibly affected by the green substance which causes the coloration of the Oyster. 

 No attempt was made to test the matter with the use of alcoholic green solutions obtained from 

 affected Oysters, as the former are not easy to get with a sufficient depth of color, because of the 

 relatively small amount of coloring matter present in the animals. Unstained (fresh) preparations 

 were used in all of these experiments. 



COLORS IN DIFFERENT PARTS. I find the liver to be normally of a brownish-red color in 

 both the American and European Oyster, sometimes verging toward green. When the flesh or 

 gills of the animal is green, the liver almost invariably partakes of this color, but in an intensi- 

 fied degree. The green stain or tincture appears in some cases to have 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 an ammoniacal solution ef that color, the effect of which 

 is to produce a result similar to double staining in green and red. The singular green ele- 

 ments scattered through the connective tissue remain equally well defined, and do not take the 

 carmine dye. I at first believed these to be parasitic vegetable organisms, and I also sup- 

 posed I saw starch granules in them, which physical tests with an iodine solution failed to con- 

 firm. These large and small green granular bodies in the connective tissue, and those close to 

 the iutestiual wall, as well as those in the heart I, find present in fewer numbers in white-fleshed 

 Oysters, but simply with this difference, that they are devoid of the green color. It is evident, 

 therefore, that they cannot be of the nature of parasites, though the color is limited to them, 

 only the surrounding tissue, except in the region of the heart, appearing of the normal tint. 

 This condition of the specimens observed by me does not, however, disprove the possibility of 

 the occurrence of vegetable parasites in the Oyster, where there is as much, or perhaps more 

 likelihood of their occurring than in some much more highly organized animals. 



It is a fact, however, that the Oyster is singularly free from true parasites of all kinds; the 



