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 



B 



C 



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

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



daughter-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- segment, 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 its 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 



