U. S. B. F.— Doc. 890. 



Plate III. 



-S> 



FIG. 1.— SPERMATOZOON OF MALE OYSTER. Magnified 1 ,700 diameters. (AfterStafford.) 



PIG. 2. OYSTER EGG. Magnified 600 diameters. 



fig'. 3.— FREE-SWIMMING LARVA OF OYSTER, ABOUT 10 DAYS OLD. Magnified 



300 diameters. 

 FIG. 4— FREE-SWIMMING OYSTER LARVA WITH VELUM, OR SWIMMING ORGAN 



EXTENDED. Magnified 300 diameters. 



(Figs. 2, 3, and 4 drawn by J. S. Gutsell.) 



