Experimental Hybridizhig 



7Z 



At one of the two maturation divisions the united pairs of 

 chromosomes separate again and move into opposite cells (Figs. 

 I and I A), so that one cell gets one and the other cell the other 

 of each of the homologous chromosomes. Thus each cell will 

 contain some paternal and some maternal chromosomes, but 

 the number of the maternal may be different from the number 



A b C d e 

 a B c D E 



Fig. 6. Scheme to illustrate the two maturation divisions as seen in the 

 spindle and chromosomes. The clear circles represent paternal chromosomes 

 and the black dots the maternal chromosomes. In the first division, represented 

 by I and I A, some of the maternal and some of the paternal chromosomes move 

 toward each pole of the spindle. In the second division each paternal and each 

 maternal chromosome divides into equal parts. In II the chromosomes of the 

 cell derived from the upper end of I and I A is represented; in II A those from 

 the lower end. 



of the paternal. At the other maturation division^ each chro- 

 mosome divides equallyFigs.il and 11^, so that the daughter 

 cells are exactly ahke.'^ Thus there will be two cells of one kind 

 in regard to the single character (or group of united characters) 

 contained in each chromosome, and two cells of the other kind. 

 The same process occurs both in the egg and in the sperm- 

 cells. In the egg three of the cells, the three polar bodies, are 



^ In some species the first, in others, the second, is the equation division. 

 ^ The meaning of this equation division has been much discussed, but nothing 

 is known about it. 



