TETRAPLOIDS 



121 



the other half to the other pole. Each daughter cell gets 

 12 chromosomes. 



The tetraploid has 24 pairs or 48 chromosomes. Prior 

 to their entrance into the first maturation spindle they 

 come together in fours (Fig. 76 and Fig. 75). The differ- 



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Fig. 75. 



Methods of conjugation of the chromosomes in diploid, triploid, 

 and tetraploid types of Datura stramonium. (After Belling and 

 Blakeslee.) 



ent ways in which these chromosomes are combined in 

 these quadrivalent groups is shown in these figures. They 

 enter the first maturation spindle in approximately this 

 condition. At the first maturation division two members 

 of each quadrivalent pass to one pole and two to the op- 

 posite pole (Fig. 75). Each pollen grain has 24 chromo- 

 somes. Occasionally, however, three chromosomes may 

 pass to one pole and one to the other. 



