﻿19 16] MERRI MAN—NUCLEAR DIVISION 32 1 



substances c and d are evolved about 5 minutes later than the first 

 appearance of a and b. Upon examining many kinds of fixed 

 material, stages were found, as shown in figs. 38, 53, and 55, where 

 polar chromatic disks similarly appear in metaphase and anaphase. 

 In some cases only chromatic granules, in place of disks, are 

 present, reminding one of centrosomes (fig. 50). 



These substances appearing at the ends of the spindle may have 

 been originally either at the border of the turbid mass seen in pro- 

 phase (fig. 5), or else may be the accumulations discharged from 

 the disk in metaphase as separate droplets (see fig. 62, from fixed 

 material). Whether of cytoplasmic or nuclear origin, they appear 

 to be of the same consistency as the disks having similar indices 

 of refraction. The ends of the spindle are now lost to view in 

 aggregations of granular matter that appear identical with the 

 earlier suspensors. As the disks a and b approach the poles, a 

 border of similar material appears, connecting them with disks 

 c and d (fig. 8). This results in two irregularly shaped figures 

 inclined to the quadrilateral, the jelly-like substance on the rim, 

 the interior grayish. 



This blending takes place before the two gels in their retreat 

 have reached the polar granular masses. The substance in c then, 

 probably contributed by the cytoplasm, rejuvenates the chromatic 

 substance, and with this blending the disks likewise lose strands 

 of their material to the cytoplasm. The changes in form and trans- 

 lucence of all substances in this stage take place with great rapidity. 

 This accounts for the great variability and amorphous appearance 

 of the separating disks as seen in prepared slides. The many 

 kaleidoscopic shif tings of these masses, as illustrated in figs. 8- 11 

 and 20-22, result in the appearance of a nucleolus within the gray- 

 ish interior of each quadrilateral, while the gel forms the rim or 

 daughter nuclear plasm. As movements subside, a reversal of* 

 optical refraction ensues, the central body appearing to increase 

 in density, while the nuclear plasm becomes optically more like 

 the hyaline cytoplasm (figs. 12, 13). 



The daughter nucleus has manifestly received accessions from the 

 cytoplasm at two periods in the karyokinesis : (1) when the sphere 

 enlarges and becomes turbid; and (2) when disk c, apparently 



