258 NEIL S. DUNGAY. 



EXPLANATION OF PLATES. 

 PLATE I. 



All figures were drawn with the camera lucida with Leitz apochromat 2 mm. 

 oil immersion objective, and Zeiss No. 6 compensating ocular, c, cortical layer. 



FIG. i. Egg fixed i hour and 20 minutes after insemination with sperm which 

 was injured by heating to 43-44 C. for 8 minutes. No jelly has formed. Periph- 

 eral alveoli still intact. Anaphase of first maturation. 



FIG. 2. Reconstruction of 2 sections of an egg from same culture as Fig. i, 

 fixed i hour and 50 minutes after insemination. Both polar bodies have been 

 formed. Peripheral alveoli still unemptied. Egg nucleus in form of scattered 

 vesicles, only part of which are seen in this figure. In all, 14 vesicles and about 

 28 nucleoli are indicated. Sperm cell (in another section) is still attached to 

 vitelline membrane. 



FIG. 3. Egg fixed i hour and 15 minutes after insemination with sperm which 

 was injured by heating to 43-44 C. for 17 minutes. Jelly was formed and both 

 polar bodies are present. Second polar body shown. Egg nucleus in form of 

 vesicles, 13 of which are indicated in the various sections. Sperm cell (in another 

 section) is still external. Strongly staining granules around periphery of egg. 



