THE CELL 19 



in a radiating manner, so that when the nucleus is viewed 

 from one end it has the appearance of a rosette or a con- 

 ventional star. This stage of the process is hence often called 

 the single star or monaster stage (fig. 3, 2). 



Each loop now splits longitudinally into two, the divisions 

 lying side by side (fig. 3, 2). 



The next change consists in the separation from one another 

 of the two halves of the split loops one half of each passing 

 up towards the one polar body, the other half passing towards 

 the other. It is the looped parts which first separate and 

 which lead the way the open ends of the loops remaining in 

 contact for a longer period, but, finally, also separating. In 

 this way, around each polar body, a series of looped fibres gets 

 arranged in a radiating manner, so that the nucleus now 

 contains two rosettes or stars, and this stage of division is 

 hence called the dyaster stage (fig. 3, 3). 



The single nucleus is now practically double. Gradually 

 in each half finer fibres develop and produce the reticular 

 appearance. Nuclear nodes, nucleoli, and the nuclear mem- 

 brane appear, and thus two resting nuclei are formed from 

 a single nucleus. Between these two nuclei a delicate line 

 appears, dividing the cell in two, and the division is accom- 

 plished (fig. 3, 4). 



The network of the nucleus of actively dividing cells is rich 

 in nucleic acid, but in cells which have ceased to divide, in 

 which the nucleus has ceased to exercise its great reproductive 

 function, the amount of phosphorus i.e. of nucleic acid 

 diminishes, and may be actually less than the amount in the 

 cell protoplasm. 



Amitotie Division. In some cells the nucleus does not 

 appear to take an active part, the cell dividing without the 

 characteristic changes above discussed. 



