REPRODUCTION 57 



which is now to take place. The chromatin 

 masses, at the centre of the spindle, now become 

 divided into two parts, each by a line of fission 

 which is at right angles to the long axis of the 

 spindle. Two groups of chromosomes are thus 

 formed which we may roughly speak of as a right 

 and a left group. Each of these now retreats 

 farther and farther from the centre and from its 

 sister group and approaches nearer and nearer to 

 the periphery and to the centrosome. 



It does not, however, actually reach this struc- 

 ture but stops short on arriving near it, so that 

 we now find on either side of the cell a group 

 of chromosomes situated to the inner side of the 

 centrosome, which chromosomes as they take up 

 this position become shorter and thicker and crowd 

 up close to one another. A wall forms around 

 each group of chromosomes, a new nucleus or pair 

 of nuclei being thus constituted, and finally a wall 

 of separation divides the two parts of the cell from 

 one another and the process of division is complete, 

 for where one cell alone existed there now are two. 

 Such a process of division, accompanied by this 

 kind of country-dance on the part of the chromo- 

 somes, is called a process of karyokinesis or of 

 mitosis and one can hardly dwell at all deeply on 

 the significance of it without coming to the con- 

 clusion that a part at least of its intention is that 



