Report U. S. F. C. 1897. (To face page 276.) 



Plate I. 



Fig. 1. Oyster with right shell and mantle removed, a and o, origin of arteries from the ventricle- 

 aw, auricle of heart; hi\ ve.ssel carrying blood from the gills to the auricle of the heart; bj outline 

 of organ of Bojanus. the so-called kidney; bp, pores from which the water issues into the branchial 

 canals after passing through the gills; d. cloaca; d, pr/.and sg. connective and two ganglia of the 

 nervous system; g, gills; gc. cavity between the two mantle folds; h, hinge; I, ligament; M ad- 

 ductor muscle; m, mouth; mt, mantle, the arrows show the direction of currents produced by the 

 cilia; /», palps; p', outer end of rigrht pedal muscle; s, external opening of sexual and renal organs 

 of right side; v, anus; ve. ventricle of heart. 



Fig. ~'. Diagram to show sexual organs of the oyster, d, duct of sexual gland. Other letters as above. 



