CHROMOSOMES OUTSIDE NUCLEUS 



and the other half towards the other centrosome 

 (figs. 56-61, 65-7). The spindle divides in the centre 

 (figs. 68-70); and lastly the cell itself divides (fig. 71). 

 In each daughter cell the chromosomes return to 

 their granular condition and pervade the whole 

 cytoplasm. The single centrosome (for there is now 

 one only in each daughter cell) again becomes tucked 

 into the centre of the transparent nucleus which 

 consists of one half of the original spindle, and thus 

 the cycle of mitosis is completed. Doubtless each 

 chromosome granule divides during some part of the 

 cycle, but owing to their minute size we have not 

 been able to see their division. 



The cells, of course, do not usually divide in 

 definite stages such as the aster and diaster, although 

 sometimes a cell will be found which presents one 

 of them. Sometimes one sees that the chromosomes 

 may be dividing in one part of the cell, while some 

 chromosomes in another part are being reconverted 

 into granules of chromatin. The way in which a 

 cell is lying on the jelly must be taken into con- 

 sideration in the determination of the stage of mitosis. 

 One rarely finds a perfect figure as described in 

 diagrammatic drawings of other types of cell, for the 

 cells frequently appear foreshortened owing to the 

 oblique manner in which they happen to come to 

 rest under the cover-glass. The position of the ring- 

 shaped nucleolus-centrosomes is of prime importance 

 in the determination of the stage of the initotic 

 figure. 



In observing any stage of mitosis, however, it will 



