570 



THE AMERICAN NATURALIST [Vol. XLIII 



chromosomes divide during the anaphase of the heterotypic 

 mitosis in preparation for the second or homotypic mitosis so 

 that they appear at the poles of the heterotypic spindle in the 

 form of three split chromosomes or pairs. 



The chromosomes change their form in the interkinesis, be- 

 coming long spiral threads which shorten on the approach of 

 the homotypic mitosis when the six chromosomes again appear 

 as three pairs showing the same characteristic range of form. 

 The members of these three pairs are distributed by this division 

 so that the nucleus of each pollen grain receives three chromo- 



be recognized in the resting nucleus by three prochromosomes. 



ported the conclusions above outlined! 



Bradley M. Davis. 



