26 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Male 

 pronudeus. 



F, 

 pronudeus. 



non-pregnant woman. 

 This process is known 

 as ovulation, 

 and continues 

 up to the time 

 of the meno- 

 pause, which appears 

 generally at the age of 

 forty-five. 



As soon as the ovum 

 is liberated from the 

 ovary, a mitotic divis- 

 ion of the nucleus 

 takes place, and the 

 ovum extrudes or pro- 

 duces what is called 

 the first polar body. 

 This is a form of bud- 

 ding, the polar body 

 receiving one-half the 

 original nucleus of the 

 ovum. Without delay, 

 a second division of 

 the nucleus in the 

 ovum takes place, and 

 a second polar body 

 is produced. This is 

 also an equal division 

 of the nucleus, but 



this time there is a Fig. 3. A, fertilized ovum of 



rpHnrtmn nf rrn^ Vialf echinus (Hertwig): the male and the 



t One-Hall female pronuc]eus are approaching; in 



the number of chro- ^ tne y nave almost fused; C, ovum of 

 echinus after completion of fertilization 



mosomes, and may be (Hertwig). 



