Coker. — Demonstration of Pearls 73 



fresh-water species, Anodonta implicata, abundant near by 

 at Onset, Mass. 



"You will recall an account of the beginnings of my 

 endeavors given at the American Fisheries Society meeting 

 of 1910, with specimens of the work then proceeding tb 

 produce pearl cysts, shown in discussing Professor Dean's 

 announcement that Professor Nishikawa had discovered a 

 method of forced pearl production. 



"In the fall of 1911, unfortunately, only two of my 

 marine specimens were recovered, only one of which had 

 been treated to produce a free pearl ; this, however, had a 

 round pearl ; and, of the fresh-water specimens examined, 

 of four western specimens, one Plcurobema ccsopus con- 

 tained a button pearl, and four free, nacreous masses were 

 obtained from nine specimens of Anodonta implicata. 

 These latter were very irregular and some flake-like, and 

 those of the marine specimen and Plcurobema ccsopus might 

 have been natural ; so, though they established in my mind 

 a belief that a method had been discovered, they did not 

 seem worthy of presentation until it had been more defi- 

 nitely established. 



"These specimens of 1912, however, about two dozen 

 in number, show a definite, free and complete pearl, in the 

 definite place treated, with such regular recurrence, that 

 there would seem to be no good basis for a reasonable doubt 

 of the demonstration of the method. Should there be any 

 question, however, I would wish to have you treat the 

 specimens in any way you see fit, by further dissection or 

 section, decalcification of the pearls, or any other method, 

 as others can readily be produced, but it is most desirable 

 that the demonstration should be satisfactory. As regards 

 the second proposition, viz., its application to the production 

 of commercial pearls in the appropriate species, there yet 

 remains much to be desired ; as to species, increased cer- 

 tainty by more accurate technique, improved sphericity, fine 

 lustre, and anatomical location giving better opportunity for 

 larger and more perfect pearls. Therefore, though some 



