22 



THE HUMAN BODY 



spindle; the achromatin filaments disappear, and the nucleus di- 

 viding in the equatorial plane, two nuclei are formed, each with 

 nucleoplasm and chromoplasm : the chromoplasm of each is de- 



B 



FIG. 10. Diagrams representing more advanced stages of karyokinesis than 

 those illustrated in Fig. 9. a, polar, and e, antipolar end of nuclear spindle; b and 

 c, portions of the chromatic filament; d, nucleoplasm; /, cell protoplasm with in- 

 dications of a radial arrangement in the neighborhood of the pole and antipole. 



The nuclear spindle is seen to have lengthened and become placed in the center 

 of the nucleus, the pole and antipole of which its ends reach. In A the Vs which 

 resulted from divisions of the chromatic filament at its antipolar loops are seen 

 to have become much shorter and thicker and to have changed position, so that 

 instead of lying lengthwise in the nucleus, with their points towards the pole, they 

 lie equatorially, with their points towards the spindle and their open ends towards 

 the periphery of the nucleus. For the sake of clearness only two are represented 

 out of the set of them which surrounds the spindle; b is still uncleft; c lias nearly 

 completed its longitudinal division into two Vs, the angle of one of which is com- 

 mencing to travel towards the pole and of the other towards the antipole. In B 

 the splitting of the Vs and the progress of their halves towards the ends of the 

 nucleus is more advanced. 



rived, as follows from the' preceding description, from both polar 

 and antipolar regions of the parent nucleus. The chromoplasm in 

 each daughter nucleus unites into a single convoluted chromatic 

 filament like that represented for the parent nucleus in Fig. 9, and 

 this filament breaks up and becomes arranged into reticulum, 

 nucleolus, and nuclear membrane as in the resting cell (Figs. 7 and 

 8). Around the new nuclei the cell-protoplasm rearranges itself 

 and divides to form a new cell-body enveloping each; during its 

 rearrangement its material frequently presents a radial structure, 

 the radii converging towards the ends of the nuclear spindle. The 

 poles of the nuclear spindle, which it will be remembered represent 



