MITOSIS 



113 



a number of segments of equal length, which may be straight 

 and rod-shaped, or curved into a horseshoe shape, or may 

 be simply spherical or ovoid masses. In some cases the 



Fig- 23. 



Diagrams representing the essential phenomena of mitosis. A , a cell with resting 

 nucleus containing a chromatic reticulum and a single nucleolus. The 

 centrosome is double and surrounded by the centrosphere. B, the centro- 

 somes are separating and each is surrounded by astral rays ; the chromatin 

 forms a convoluted thread or spireme. C, The spireme is broken up into a 

 number of V-shaped chromosomes, the polar spindle is formed between the 

 now widely separate centrosomes. /?, The chromosomes attached to the 

 spindle-fibres are arranged at the equator of the spindle. E, division of the 

 chromosomes, which are viewed end on. f, divergence of the chromosomes. 

 G, chromosomes collecting at the poles of the spindle, the space between 

 them occupied by interzonal fibres ; commencement of division of the cell- 

 body. H, /, complete division of the cell, and reconstitution of the nuclei. 

 In / the centrosomes are dividing preparatory to a new mitosis. Note 

 A-D-propha.se; .=metaphase ; F, (7 = anaphase. H, /=telophase. 



curved rods may be joined together by their ends to form 

 rings. But their shape is relatively unimportant, the essential 

 thing is that the chromatin is resolved into a definite number 



