68 



THE MATURATION OF THE EGG OF THE MOUSE. 



21. Each spindle is oblique to the surface of the egg at the beginning 

 of the abstriction of its polar cell. 



22. All eggs form two spindles and a first polar cell. 



23. All seminated eggs form a second polar cell. 



24. The first polar cell probably migrates in the peri vitelline space 

 inside the zona pellucida, and is aided in this movement by the process 

 of ovulation. 



25. The first polar cell may or may not degenerate. 



26. Maturation division in the mouse egg belongs to the type known 

 as prereduction division. 



