191(5] Wilson: On the Lifc-Historij of a Soil Amoeba 253 



After the separation of the chromosomes is completed, the parts 

 of the spindle gradually resume their original place in the resting 

 nucleus. In each daughter nucleus fused chromosome and chromatic 

 polar masses become the chromatin of the new karyosome. Remains 

 of the central spindle and of the spindle fibers, centrioles, and perhaps 

 some of the pla.stiu of the chromatic polar mass, become the centro- 

 desmose, or central "vacuole," of the new karyosome, while the 

 chromatin net is extruded from the region between the chromosome and 

 chromatic polar masses to become the peripheral chromatin (pi. 18, 

 figs. 12, 15; pi. 19, figs. 17, 25; pi. 20, figs. 43, 46, 50, 51, 53, 57, 61). 



Upon each of the eight spindle fibers one chromosome is formed, 

 the source of the chromatin of which has been a disputed matter. 

 Some de.scribe it as coming entirely from the karyosome, some as coming 

 entirely from the peripheral chromatin, while Alexeieff (1911) says 

 that it comes from both. The evidence of the material used in this 

 work is in support of the last view, and it falls into four heads, a.s 

 follows : ( 1 ) the character and behavior of the peripheral chromatin ; 



(2) character of the spindle fibers and staining of the equatorial plate ; 



(3) the occasional occurrence of large granules with variable staining 

 capacity continuous with those of the karyosome; and (4) the behavior 

 of the chromo.some mass and extrusion of chromatin net in reorganizing 

 nuclei. 



Part of this evidence has already been discussed, and for that 

 reason will be given only briefiy here. In some early prophase figures 

 there are to be found, between the nuclear membrane and karyosome, 

 granules which take the chromatin stain (pi. 20, figs. 39, 40). This 

 indicates that chromatin is present in the peripheral mass, though 

 generally it is too diffuse to hold the stain. All the peripheral mass 

 comes onto the karyosome, becoming more fibrillar as it does so. The 

 fibers are somewhat granular in appearance, but do not take the stain 

 of chromatin at any point. The uu.staining thickenings of these take 

 up their position in a regular equatorial plate, each fiber having at its 

 middle a mass evidently made up of several granules (pi. 18, fig. 9) 

 which later fuse into a deeply staining chromo.some, all of the chromo- 

 somes of a spindle being regular and subequal (pi. 18, fig. 7). These 

 chromosomes could have come from the diffusion of chromatin from 

 the karyosome, except that this view leaves the peripheral granules out 

 of account. 



On the other hand, a large part of the chromosome material may 

 come from the karvosome, since the total quantity in each is in- 



