CAUSE OF THE CIM.KN COLOR OF THE OYSTER. 7:;;. 



There is therefore no doubt hut that a delicate balance of power is maintained by these rivals 

 which is best fur tin- health of tin- community. The stabilitx of permanent o\ sicr l.c.K, it must 

 lie remembered, t'lirnislics ilic right conditions for the survival of many types. It is a place where 

 tli. \ tind lioth a home and pleat}" of food. It is the very fa vonibleness offered by tlu.se places 

 which tends to induce them to congregate and multiply, and it becomes a serious question whether 

 the artilicial establishment of banks will not in time cause the proper. types to congregate and 

 multiply so as to Milord the needed food supply for the Oysters. That destructive members of the 

 community may also he attracted is admitted, but if the beds are established in shallow waters, as 

 I have pieviously suggested, the destruction of such unwelcome intruders may be very readily 

 c Heeled. Drills" and boring-sponges are naturally to be thought of a types which should be 

 destroyed, while diatoms, infusoria, small polyps, bryozoa, minute alga?, etc., are to be favored in 

 CM -:-\ wa\. Those forms again which the oyster-culturist knows are only there for the purpose 

 of -jetting a good living with little trouble to themselves ought to be destroyed. 



It might be an advantage to introduce certain desirable forms onto a bank, which might be 

 supposed to be useful as a food supply. Infusoria and diatoms not previously existing might be 

 introduced in this way; this, I think, would be especially easy in the case of the former where 

 the tyi>e was one which is fixed during its adult life. 



216. ON THE CAUSE OF THE GREEN COLOR OF THE OYSTER. 



EXPERIMENTS AT WASHINGTON AND PHILADELPHIA. I have frequently read accounts of 

 Oysters which had become green-fleshed in certain localities, and it has also been asserted that 

 competent chemists had discovered poisonous green substances of metallic origin in such s|tuci- 

 moils. Tests made at the Smithsonian Institution by Professor Endlich in 1879 failed to disclose 

 anything poisonous in some green Oysters which had excited the suspicion of the Board of Health 

 of the city of Washington. This investigator, it is desirable to state, resorted to every test known 

 to him in order to discover if anything poisonous was present, and failing to discover any harmful 

 substance concluded that the color must be due to some inert material. In order to set; if tin- color 

 was due to the presence of some green compound of copper, Prof. H. C. Lewis, of the Academy of 

 Natural Sciences of Philadelphia, kindly made some delicate tests for me, using small dried frag- 

 ments of an Oyster very deeply tinged with green in various regions, especially in the liver, con- 

 nective tissue, and mantle. The fragments were burned in a bead of microcosmic salt and chloride 

 of sodium on a clean platinum wire in a gas dame; this test did not give the characteristic sky- 

 blue flame which should have been developed had there been the minutest trace of copper present. 



It is therefore clear that the substance, whatever it may be, is not a corrosive metallic poison 

 derived from copper, which if present would almost undoubtedly be detected by a peculiar acrid 

 metallic taste, which would be experienced when one ate eucu Oysters. In making some practic.il 

 tests as to the relative qualities of such Oysters as compared with white Meshed ones. op|M>r 

 tunities for which were kindly furnished me by Mr. J. M. Carley, of Fulton Market, I faded to 

 detect the slightest difference of flavor. Such also is Professor Leidy's verdict, who informs 

 me that he made a similar experiment, and a restaurateur, with whom I discussed the matter, 

 declared that he was in the habit of selecting them for his own eating, preferring their flavor to 

 that of the white O.. store. 



VARIATIONS IN COLOR. If it be objected that the green color indicates an unhealthful 

 condition of the animal, it may be stated that other color variations of the flesh have fallen 



