BULLETIN OF THE UNITED STATES FISH COMMISSION. 181 



41. -ON THE GBEi:iV COLORATION OF THE GILLS AND PALPS OI' 



THE CLAM (MVA AKENARIA). 



By JOHL\ A. BVDEK. 



Mr. W.Williams, collector of the port at Stoniugton, Conn., recently 

 forwarded from there five specimens of tbe common clam to Professor 

 Baird, with the request that he would have them examined and report 

 upon tbe nature and source of the pigment which tinged the gills and 

 palps with a disagreeable bluish-green color. In his letter of December 

 31. 18S4, Mr. Williams says: " 1 forward you this day some clams for 

 examination, [in order to ascertain] the cause of the 'greening,' as per 

 your letter of November 28, 1884. Parties here are afraid to use them 

 on account of the ' greening.' Will you please report, so I can have your 

 answer published and settle the question [raised] as to their unhealth- 

 fuluess as food ? " 



Strangely enough — in spite of the fact that it has been repeatedly 

 stated by competent chemists, such as Berthelot,* Endlich,t and others 

 that chemical research had failed to detect metallic substances such as 

 copper — dealers, oystermeu, and the public still persist in holding to the 

 belief that there is really some green metallic salt of copper present, 

 as evidenced by the fact that oysters when "green-gilled" have a cop- 

 pery taste. The experiments of Puysegur and Decaisne ha've shown 

 how groundless this belief is, and have demonstrated beyond a shadow 

 of doubt that if the proper food material was selected and brought 

 within reach of the living animals, other food being excluded, they could 

 cause individuals, the flesh of which was known to be colorless before 

 the experiment was tried, to become greenish. These same animals, 

 when subsequently deprived of what might be called their viridigenous 

 diet of Naricula ostrearia, variety fusiformis, lost their viridity entirely 

 in a few days and again became white-fleshed. 



This viridity I have noticed in living oysters sent me from France 

 and England. Three species similarly affected, that is, with the gills, 

 heart, or mantle more or less discolored by the absorption of a soluble 

 pigment alluded to elsewhere,! have fallen under my observation. 



MM. Puysegur and Decaisne have traced the viridity which discolors 

 the flesh of the oyster to its source, and, as stated above, have experi- 

 mentally proved that it could be artifically induced and removed under 

 the requisite conditions. The writer's share in completing the history 



* See Ann. Report U. S. Commissioner of Fish and Fisheries, Part X, 1882, p. 793, 

 il On the Cause of the Greening of Oysters," by M. Puysegur. 



t'Bnll. U. S. Fish Commission, I, 1881, p. 413, in "Notes on the Breeding, Food, and 

 Green Color of the Oyster." 



t Ann. Report U. S. fish Commissioner, Part X, 1882, pp. 801-805, "Supplementary 

 Note on the Coloration of the Blood Corpuscles of the Oyster " ; also in Am. Nat 

 uralist, 1883, pp. 87, 88. 



