GROWTH AND CELL DIVISION 



75 



daughter nuclei. Although the changes which the chromatin 

 undergoes during prophase are coincident with the building of 

 the spindle, it is easier and clearer to discuss the chromatin 

 changes and the origin of the spindle separately. We are already 



FIG. 42. Drawings illustrating the main stages in mitosis 



a-e, prophase ; /, metaphase ; g, anaphase ; h-i, telophase ; j-k, cell division ; 

 I, daughter nuclei 



familiar with the fact that the chromatin in the nucleus of a rest- 

 ing cell is in the form of a net, or meshwork. In early prophase, 

 when the nucleus begins its preparation for division, it may be 

 noted that the chromatin granules begin to accumulate along 

 definite portions of the resting network, thus giving rise to denser 

 masses of chromatin at certain points (a). These dense masses 

 of chromatin, which are at first irregular, ultimately assume a 



