CELL-DIVISION 



25 



ispended in the linin network (long regarded as a mere 



Fig. 6. Changes in nucleus and cell in indirect (mitotic) nuclear division. A, resting 

 nucleus with two centrioles l in single centrosphere (c) ; B, centrosphere divided, 

 spindle and two asters (a) forming ; C, centrospheres separated, nuclear wall 

 disappearing ; D, resolution of nucleus into chromosomes ; E, mature plasmic 

 spindle, with longitudinal fission of chromosomes ; F, chromosomes forming 

 equatorial plate (ep) of spindle. (From Wilson.) 



nucleole). Such a nucleus is often termed a " vesicular 

 nucleus. 2 



1 The " centriole " is a minute granule sometimes recognisable in the centre of the 

 centrosphere, and undergoing fission in advance. But centrosomes are often found 

 without a distinction into centrosphere and centriole, and there is much confusion 

 in the use of the terms. 



2 For a detailed study of the nucleus in Protista, see Calkins in Arch. Protistcnk. 

 vol. ii. 1903. 



