THE MEIOTIC DIVISION 



21 



made up of two chromosomes joined end to end. 1 When 

 these pairs of chromosomes are differentiated they become 

 attached to the spindle fibres just as happened in the case 

 of the somatic chromosomes. Instead of splitting length- 

 ways, however, the two chromosomes forming each pair are 

 pulled apart, one whole chromosome going to one pole of the 

 cell, and the other whole chromosome going to the other 

 pole (Fig. 13). This form of division results in the pro- 

 duction of two daughter cells, each having half the number 

 of whole chromosomes that were present in the mother cell. 

 It has been called the meiotic division. Thus, if we imagine 



FIG. 12. Early stage in the 

 meiotic division. 



FIG. 13. The pairs of 

 chromosomes sepa- 

 rating in the meiotic 

 division. 



an organism with four chromosomes, and call these chromo- 

 somes A, B, C, and D, in this reducing division two daughter 

 cells will be produced, one possessing the chromosome A 

 and B, the other C and D, or of course any other combina- 

 tion of A, B, C, and D in pairs (see Fig. 15). Taking the 

 same organism to illustrate the division in the somatic 

 or body cell, each of the daughter cells produced would of 

 course contain an accurate longitudinal half of each of the 

 four chromosomes A, B, C, and D (see Fig. 14). 



We have seen that the number of chromosomes in the 

 cells of any given organism remains the same from genera- 

 tion to generation of new individuals. We have also seen 



1 See note on nieiotic phase at end of chapter. 



