50 



CELL-DIVISION 



disappears, and the two asters pass to opposite poles of the nucleus 

 (most plant mitoses and in many animal cells). A spindle is now 

 formed from rays that grow into the nucleus from each aster, the 

 nuclear membrane fading away at the poles, though in some cases it 

 may be pushed in by the spindle-fibres for some distance before its 



Fig. 20. — Diagrams of the later phases of mitosis. 

 G. Metaphase ; spHtting of the chromosomes {e. p.) ; «. The cast-off nucleolus. H. Ana- 

 phase; the daughter-chromosomes diverging, between them the interzonal fibres (/./), or central 

 spindle; centrosomes already doubled in anticipation of the ensuing division. /. Late anaphase 

 or telophase, showing division of the cell-body, mid-body at the equator of the spindle and begm- 

 ning reconstruction of the daughter-nuclei. J. Division completed. 



disappearance (Fig. 19, C, E). In this case there is apparently no 

 central spindle. In a few exceptional cases, finally, the amphiaster 

 may arise inside the nucleus (p. 225). 



The entire structure, resulting from the foregoing changes, is 

 known as the karyokinctic or mitotic fiirurc. It may be described as 

 consi-sting of two distinct parts; namely, i, the chromatic figure, 

 formed by the deeply staining chromosomes ; and, 2, the achromatic 



