72 American Fisheries Society 



used as mentioned — the common oyster, the hard clam or 

 Quohaug, and a thin-shelled fresh-water form, Anodonta 

 implicate! — and this is the material which is available for 

 your observation today. 

 The material is as follows : 



( 1 ) Specimens of the anterior adductor muscle of 

 Venus mercenaries showing partially dissected free and com- 

 plete pearls of forced production (1 year's growth). 



(2) One of two living specimens recovered of our edible 

 oyster, Ostrea virginica, showing free and complete pearl 

 embedded in the anterior adductor muscle — induced by me- 

 chanical means. 



(3) Several specimens of the anterior adductor muscle 

 and one of the body of Anodonta implicata (from Quissett, 

 Mass.) showing partially dissected free and complete pearls 

 of forced production. 



(4) Specimens of minute, round pearls and a "point" 

 from Venus mercenaria — forced production, together with 

 free, nacreous masses from body and muscle of Anodonta 

 implicata. 



(5) Two shells of the common edible oyster, one con- 

 taining approximately round pearl, pearls formed in the 

 adductor muscle and attached to the shell at the adductor 

 impression. The pearl in each case is supposed to have 

 been formed free and to have acquired a secondary attach- 

 ment to the shell. 



Dr. Herrick permits the following quotation from his 

 letter : 



"Several common and easily secured species were se- 

 lected for experimentation that the comparative physiology 

 might aid ( 1 ) in demonstrating a method of forced free 

 and complete pearl production, (2) which might be applied 

 to the production of commercial pearls by the appropriate 

 species. Therefore, of these specimens some are from the 

 marine species Ostrea virginica (our edible oyster) and 

 Venus mercenaria (the hard-shelled clam), others from a 



