THE CELL AND PROTOPLASM. 



Ill 



the male and female chromosomes perhaps always 

 remaining distinct. 



While this mixture of chromosomes has been 

 taking place the centrosome has divided into two 

 parts, each of which becomes surrounded by an 

 aster and travels to opposite ends of the nucleus 

 (Fig. 42). There now follows a division of the 

 nucleus exactly similar to that which occurs in 

 the normal cell division already described in Figs. 

 28-34. Each of the chromosomes splits length- 

 wise (Fig. 43), and one half of each then travels 

 toward each centrosome to form a new nucleus 

 (Fig. 44). Since each of the four chromosomes 



FIG. 43. FIG. 44. 



FIG. 43. An equatorial plate is fo med and each chromosome has 



split into two halves by longititudinal division. 

 FIG. 44. The halves of the chromosomes have separated to form 



two nucleii, each with male and female chromosomes. The egg 



has divided into two cells. 



thus splits, it follows that each of the two daugh- 

 ter nucleii will, of course, contain four chromo- 

 somes; two of which have been derived from the 

 male and two from the female parent. From now 

 the divisions of the egg follow rapidly by the nor- 

 mal process of cell division until from this one 

 egg cell there are eventually derived hundreds of 



