THE FUNDAMENTAL PHYSIOLOGICAL ACTIONS. 21 



pole, the other towards the antipole. The whole nucleus 

 elongates in the direction of the long axis of the spindle; the 

 achromatin filaments disappear, and the nucleus dividing in 



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, por- 

 tions of the chromatic filament; rf, nucleoplasm; /, cell protoplasm with indications 

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



The nuclear spiudle is seen to have lengthened and become placed in the centre 

 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 in- 

 stead 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; 6 is still uncleft; c has nearly com- 

 pleted its longitudinal division into two Vs, the angle of one of which is commencing 

 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. 



the equatorial plane, two nuclei are formed, each with nucleo- 

 plasm and chromoplasm : the chromoplasm of each is derived, 

 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 chro- 

 matic 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 fre- 

 quently presents a radial structure, the radii converging to- 

 wards the ends of the nuclear spindle. The poles of the nuclear 

 spindle, which it will be remembered represent the halves of 



