DEVELOPMENT OF THE OYSTER. 



Explanation of Plate XL. 



Figure 43. Dorsal view of an embryo six days old, swiinmiiig l>y the cilia of its velum. 



Figure 44. View of right side of another embryo at the same stage; m it, muscles; I, liver. Other letters as in 

 Figure 41. 



Figures 45 to 47. Views of embryo. 



Figure 48. The seminal fluid of a ripe male oyster, mixed with water, and seen with a power of 80 diameters. 

 Zeiss, a. 2. 



Figure 49. Fluid from the ovary of a ripe female oyster, seen with the same magnifjing power. 



Figure 50. Seminal fluid of a ripe male oyster, magnilied 300 diameters. 



Figure 51. Egg a few minutes after mixture with the male fluid, magnified 500 diameters. 



Figure 52. Egg about thirty minutes after fertilization, magnified 500 diameters. 



