212 J. MCA. KATER. 



It is well to emphasize at this point an interpretation of the 

 linin strands which, doubtless has already occurred to the reader. 

 The fact that they invariably run inward from the indentations 

 on the surface of the chromatin mass which represent the points 

 of contiguity of adjacent chromosomes strongly indicates that 

 they as well as the superficial indentations, represent the line of 

 contiguity of adjacent chromosomes. This also supports the 

 conception of chromosome structure held by many zoologists, 

 notably Conklin, that the chromosome consists of a linin bag 

 tilled with chromatin. Achromatic globules appear in the chro- 

 matin groundwork of the interior of the chromosomes while the 

 linin bag remains unaltered, except for the swelling due to increase 

 of material within it. At this early stage of reconstruction there 

 is no evidence whatever for the existence of linin strands within 

 the external chromosomal sheath (Fig. 3). 



The process of vacuolization normally continues until about 

 three fourths of the length of the chromosome contains a large 

 part of achromatic material, the so-called granules of chromatin. 

 occurring principally along the linin strands. The distal fourth 

 of the chromosome is still a solid mass of chromatin and so it 

 remains until the reconstruction of the nucleus is complete 

 (Fig. 4). The imbibition of achromatin by the proximal ends 

 of the chromosomes has not yet been completed. This con- 

 tinues and causes the increase in size of the daughter nucleus up 

 to the time when it ceases swelling and enters the interphase or 

 the resting period. 



Since the distal fourth of the chromatin mass does not take 

 up achromatin, it does not increase in size in harmony with the 

 proximal portion of the chromosomes, and the latter tends to> 

 swell out over it and, as it were, to engulf it. This causes the 

 [inin strands, representing fines of contact of chromosomes, to- 

 change their position, and r ceasing to be parallel to the long, 

 axis of the cell, they become radiating strands with the non- 

 vacuolized chromatin mass as their center. At the same time 

 the solid distal ends of the chromosomes tend to clump. Fig. 4 

 illustrates a cell in which the daughter nuclei still have the non- 

 vacuolized portion of every chromosome distinctly separated. 

 From this point on they start joining so that nuclei may be 



