74 The Third and Fourth Generation 



the fertilized egg would have twice as many 

 chromosomes as either parent. This doubling 

 process would continue generation after genera- 

 tion and soon give us an incalculable number. 

 During the production of the eggs and sperm 

 from the germ mother-cells in most animals, 

 and in the production of the spores from the 

 spore mother-cells in plants, there is one 

 division when, instead of the usual number of 

 chromosomes appearing in the equatorial plate 

 (Fig. 7, F), only half that number appears, but 

 these are apparently double chromosomes. 

 When they divide to form the new nuclei, the 

 chromosomes that form the doublets go to 

 separate cells. By this "reduction" division in 

 place of the customary "equation" division the 

 daughter-cells have unlike chromatin material. 

 Thus if we number the chromosomes i, 2, 

 3, 4, then the equation division would give to 

 each daughter-cell one-half of each; but the 

 reduction division might give to one daughter- 

 cell any two, as i and 3, and to the other 

 daughter-cell the others, 2 and 4. When the 

 egg and sperm come together in fertilization, 



