245 



but rather enable the naturalist to distinguish clearly his species. 

 He alluded to chemistry, in which there was a time when plati- 

 num and other silver-like metals were not distinguished from 

 silver ; but in the progress of science they were ascertained to be 

 separate and distinct species. 



Prof. Rogers replied that this argument would answer equally 

 w^ell for the other side of the question ; for instance, chemistry 

 has reduced to one many supposed different species, as the dia- 

 mond, plumbago, and carbon. 



Dr. Bryant placed upon the table forty specimens of 

 Brazilian birds mounted by himself, about half of them 

 new to the cabinet, and some of them rare ; from the 

 collection presented by Dr. J. C. Reinhardt. 



A letter from Mr. Charles W. Holman, requesting the 

 Proceedings of the Society for the library at Westeras, 

 Sweden, was referred to the Publishing Committee. 



Mr. Charles F. Eschweiler, of Houghton, Michigan, 

 was chosen a Corresponding Member, and Dr. George 

 Russell, of Boston, a Resident Member. 



March 21, 1860. 

 The President in the Chair. 



Mr. Whittemore read a communication from Mr. 

 James Lewis, of Mohawk, N. Y., on the colors of the 

 nacre of freshwater bivalves. 



In some sections of the country the nacre, ordinarily white, is 

 colored, especially in the Uhios ; from experiments made on 

 shells, he is inclined to believe that a minute trace of gold in the 

 water may in some way be connected with the rich colors of the 

 nacre of some Unios. 



