Fig. 1. — Mature egg ready for union with male cell. Magnified 600 diameters. 



Fig. 2. — Spermatozoa (male cells). Note length of tail and variation in shape 

 of head. The spermatozoon on the left is the most common form. No attempts 

 were made to study the minute anatomy. Magnified 600 diameters. 



Fig. 3. — Compressed egg. Shape due to pressure of eggs within ovary. 

 Shortly after extrusion it becomes spherical. Magnified 600 diameters. 



Fig. 4. — Egg enclosed in membranous case. Magnified 600 diameters. 



Fig. 5. — Egg, forty-three minutes after fecundation, showing the yolk lobe 

 (yl) and two polar cells (pc). The formation of the yolk lobe has given to the egg 

 a pear-shaped appearance. Magnified 600 diameters. 



Fig. 6. — Ring of spermatozoa with radiating tails held away from the egg by 

 a membrane. The entire suiface of the membrane is covered by the sperma- 

 tozoa, but only those in one plane are here shown. Magnified 600 diameters. 



Fig. 7. — Two-celled stage, forty-six minutes after fecundation, showing unequal 

 division. The larger cell contains the yolk lobe (yl) . Magnified 600 diameters. 



Fig. 8. — Four-celled stage, sixty-seven minutes after fecundation. Magni- 

 fied 600 diameters. 



