54 WHAT IS LIFE 



parts, but in the majority of instances, and invari- 

 ably in the case of the cell from which a new 

 individual is to be built up, a singular series of 

 events takes place of which some mention must 

 now be made. 



In a previous chapter the structure of the 

 nucleus and cell in what is often called, though the 

 term is a misleading one, the "resting stage" has 

 been described and it will not be necessary to re- 

 capitulate the facts there laid down. 



Prior to the division of the cell the linin of the 

 nucleus, or most of it, becomes broken lip into a 

 series of threads on which the particles or granules 

 of chromatin arrange themselves along the threads 

 like so many beads on a string (see fig. iii.). Then 

 each bead splits into halves and as the linin thread 

 at the same time flattens out, the appearance comes 



DESCRIPTION FOE FIG. III. ON PAGE 55. 



A. Resting cell with reticular nucleus and true nucleolus ; at c 

 the attraction-sphere containing two centrosomes. B. The chromatin 

 formed into a continuous tape, nucleolus present, amphiaster (a) 

 formed around centrosomes. C. Spindle-shaped karyokinetic figure 

 formed, consisting of two centrosomes with radial arrangement of 

 protoplasm around each, equatorial plate (e.p.) of chromosomes in 

 centre. D. The equatorial plate (e.p.) has split longitudinally (ri) 

 the cast-off nucleolus. E. The two sets of chromosomes are diverging 

 and the interzonal fibres (i.f.) lie between them, the central spindle. 

 The centrosomes are already doubled in anticipation of the next divi- 

 sion. F. The cell-body has divided and the two groups of chromo- 

 somes are in process of reconstructing themselves into nuclei. G. 

 Completion of the process of division. Two cells, with fully consti- 

 tuted nuclei and centrosomes take the place of the single cell shown 

 in A. From WILSON. 



