CHROMOSOMES 233 



chromosomes now change their position so that they 

 come to lie in the plane of the equator of the spindle, 

 and about this time, but sometimes earlier, each 

 chromosome splits longitudinally into two equal 

 portions (Figs. 22, 23). This splitting in the case of 

 each chromosome takes place in the equatorial plane 

 of the spindle, so that one member of each pair of 

 daughter chromosomes faces towards one pole of the 

 spindle, and the second towards the other pole. The 

 members of each pair of daughter chromosomes now 

 begin to move away from one another towards the 

 two poles of the spindle, and as they do so the first 

 indication of a dividing wall between the two new 

 cells begins to make its appearance in the equatorial 

 plane. 



Arriving at the poles, the daughter chromosomes 

 begin to elongate, and to put out processes which 

 finally meet and fuse with those of their neighbours 

 to form the chromatin reticulum of the new nuclei 

 (Fig. 25). Surrounding each new nucleus, thus 

 developing at either pole of the now rapidly dis- 

 appearing spindle, a new nuclear membrane makes its 

 appearance ; the dividing wall in the position of the 

 equator of the spindle develops into a complete 

 partition (at least in the case of plants, in which, 

 however, a number of minute passages are left pene- 

 trating the cell wall and preserving the communication 

 between the protoplasmic contents of the separate 

 cells) ; and the division into two new cells is thus 

 completed (Fig. 26). Each new cell is provided with 

 a nucleus into which has entered precisely its fair 



