l8 WEBB : DI-MYARIA\ STAGE OF THE " NATIVE " OYSTER. 



Horst, from which Figure A was probably taken, and the 

 specimens show the general anatomy in greater detail than the 

 writer's preparations, enabling one to locate the structure alluded 

 to, with greater distinctness. In another fine preparation, looked 

 at from the mouth side, the outline of the chamber, into which 

 the other end of the alimentary canal opens, can be made out, 

 together with a transverse thickening, slightly striated, on the 

 side towards the mouth in the position that should be occupied 

 by the posterior adductor (PI. I., Fig. 2, /. ndd.). 



add. 



Figure C. An embryo of the American oyster, Ostrcci vtrginiana. Lister, 

 after attachment, seen as Figure A. g. gill; m.h. mantle border; //. palps ; 

 /. add. posterior adductor. Other lettering as in Figure A. (After lh\ JacksonJ 



The conclusion is, therefore, that the structure just described 

 corresponds with that seen from the side view, and represents 

 the posterior adductor in an incipient condition. During the 

 next summer the writer hopes to be able to trace its development 

 till it becomes functional, and spat growth begins. 



