CHROMOSOMAL YI.MC1.KS IN H I ASKOLUS. 211 



subject is the uniformly small size of the short rod-like chromo- 

 somes. As is usually the case with chromosomes of this kind 

 they migrate to the poles with their long axis parallel to the Ion- 

 axis of the spindle and the advancing chn nii-^oines are so evenK 

 placed on the spindle that an almost perfect ring is formed. 

 This perfect order is maintained after the daughter chromosomes 

 come in contact with each other at the poles and at the time 

 when the apparent fusion occurs the chromosomal mass appears 

 as a rectangle with its greatest dimension at right angles to the 

 long axis of the spindle. At this time the outlines of the chrome- 

 somes are not clear and we can recognize the individual chromo- 

 somes only by the corrugation on the sides of the rectangle. The 

 rounded ends of the chromosomes prevent their tips from coming 

 in contact with each other and are responsible for the corrugations 

 on the margins of the mass of chromosomes (Fig. i). Shortly 

 after the appearance of globules of achromatic material in the 

 chromosomes the notched edges of the chromatin mass disappear 

 and the outline of the reconstructing nucleus becomes smooth. 



In rare instances the chromosomes are not perfectly parallel 

 when they become contiguous w r ith each other at the poles. In 

 such cases the chromatin mass is not as regular as described 

 above. 



Figures 2 and 3 make a very important point for this descrip- 

 tion. Fig. 2 illustrates the beginning of vacuolization in one of 

 the daughter nuclei, and in the other the vacuolization has pro- 

 ceeded to such an extent that distinctly clear areas are appearing 

 in the proximal l ends of the chromosomes. 



This figure also shows that the achromatic globules occur 

 between the indentation on the proximal surface of the nucleus 

 and that a linin strand runs inward from the indentation and 

 joins that part of the chromatin mass which has not yet taken 

 up achromatic material. A little later in the process of recon- 

 struction the proximal side of the nucleus becomes less chromatic, 

 the vacuolized portion of the chromosomes being more extensive. 

 The indentations, especially on the proximal surface, are still 

 quite pronounced and linin strands extending inward from them 

 are also prominent. 



1 Throughout this paper the ends of the chromosomes towards the equator oi 

 the spindle will be termed "proximal," while the opposite end will be called 

 "distal." 



