118 THE STORY OF LIFE'S MECHANISM. 



have reached the opposite poles of the nucleus, 

 and an equatorial plate is formed. It is not 

 infrequent, however, for it to occur at a period 

 considerably earlier, so that the chromosomes 

 are already divided when they are brought into 

 the equatorial plate. 



At some period or other in the cell division 

 this splitting of the chromosomes takes place. 

 The significance of the splitting is especially 

 noteworthy. We shall soon find reason for 



FIG. 81. FIG. 32. 



FIG. 31. Stage showing the two halves of the chromosomes separated 



from each other. 

 FIG. 32. Final stage with two nuclei! in which the chromosomes have 



again assumed the form of a network. The cenlrosomes have 



divided preparatory to the next division, and the cell is beginning 



to divide. 



believing that the chromosomes contain all the 

 hereditary traits which the cell hands down from 

 generation to generation, and indeed that the 

 chromosomes of the egg contain all the traits 

 which the parent hands down to the child. 

 Now, if this chromatin thread consists of a series 

 of units, each representing certain hereditary 

 characters, then it is plain that the division 



