66 



STAGES IN BINARY FISSION 



formed (Fig. n, B) : the chromatin, at first arranged in a coil 

 (A), breaks up, and its segments become arranged along the 

 equator of the spindle (B), divide transversely (c) and travel 

 to the poles (D E), where they form the chromatin-coils of 

 the daughter-nuclei. At the same time the fibres of the 

 spindle give rise, across the equator of the cell, to a cell- 



FIG. II. Stages in the binary fission of a plant cell. 

 A, cell with resting nucleus. 



B D, formation of nuclear spindle and division of chromatin. 

 E, reconstruction of daughter nuclei and formation of cell-plate. 

 (After Strasburger). 



plate (E) along which division takes place. But in the plant- 

 cell the cell-plate gives rise to a partition wall of cellulose 

 which divides the two daughter-cells from one another. 1 



1 The nucleoli of the plant-cell appear to be independent of the 

 chromatin of its nuclear thread, from which they differ markedly in 

 structure. They disappear during karyokinesis, and it seems probable 

 that they are active agents in the formation of the cell-wall. 



