GENERAL OUTLINE 



237 



without further change. The egg-nucleus is now ready for union 

 with the sperm-nucleus. 



D 



\ — P-^-^ 





E H 



Fig. 116. — Diagrams showing the essential facts in the maturation of the egg. The somatic 

 number of chromosomes is supposed to be four. 



A. Initial phase; two tetrads have been formed in the germinal vesicle. B. The two tetrnds 

 have been drawn up about the spindle to form the equatorial plate of the first polar mitotic 

 figure. C. The mitotic figure has rotated into position, leaving the remains of the germinal 

 vesicle at g.v. D. Formation of the first polar body; each tetrad divides into two dyads. 

 E. First polar body formed ; two dyads in it and in the egg. F. Preparation for the second 

 division. G. Second polar body forming and the first dividing; each dyad divides into two 

 single chromosomes. //. Final result; three polar bodies and the egg-nucleus (9), each con- 

 taining two single chromosomes (half the somatic number) ; c. the egg-centrosome which now 

 degenerates and is lost. 



