THE VITAL PHENOMENA OF THE CELL 



187 



Third Stage of Division. 



The third stage is characterised by the division of the single 

 group of mother-segments in the equatorial plane into two groups 

 of daughter-segments, which retreat in opposite directions from 

 one another, until they are situated in the neighbourhood of the 

 two poles of the nuclear figure (Fig. 80 A, B, C). The two 



FIG. 80. Diagrammatic representation of nuclear segmentation (after Flemming). The 

 daughter-segments are retreating in two groups towards the poles. (From Hatschek.) 



da ughter- stars are formed, as Flemming expresses it, from the 

 mother-star. The details of the process, which can only be ob- 

 served with difficulty, are as follows : 



The daughter-segments, which have been produced by the 

 splitting of a mother-seg'ment, separate from one another at the 

 angle of the loop, which is directed towards the spindle, and com- 

 mence to retreat towards the poles, whilst for a time the ends of 

 the arms of the loop remain undivided. Finally these also split 

 up. From out of the 24 original loops two groups, each contain- 

 ing 24 daughter-loops, have developed ; these move towards the 

 centrosomes, until they come quite close to them, when they 

 stop, for they never actually reach the poles themselves. Be- 

 tween these two groups fine " connecting fibrils " stretch ; these 

 are probably derived from the spindle fibrils. 



Each loop, or daughter-segment, has "its angle directed towards 

 the pole, whilst it.s free ends are turned either obliquely, or per- 

 pendicularly, to the equatorial plane." As might be expected, to 

 start with, they are much thinner than the mother-segments; 

 however, they soon begin to shorten and to become proportion- 

 ately thicker. When the daughter- star is first formed, the 

 segments lie somewhat far apart, but they soon begin to draw 



