THEORIES OF HEREDITY 



maturation half the number of chromosomes. What is 

 the reason for this reduction of chromosomes ? It is 

 evident that, as soon as reproduction takes place by the 

 union of two sex-cells, each of which contains the full 



Father. 



Mother. 



Offspring. 



I. Generation. 



II. Generation. 



III. Generation. 



IV. Generation. 



FIG. 38. COMBINATION OF IDANTS. 

 (From Weismann, " The Germ-Plasm."} 



number of chromosomes, the resulting mother-cell would 

 have double the number of chromosomes. If this process 

 went on for any length of time the number of chromosomes 

 would multiply enormously, and soon not be able to find 

 room within the nucleus. The reducing division then has 



9 



