CELL-DIVISION 



25 



suspended in the linin network (long regarded us a mere 



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

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

 spindle and two asters («) forming ; C, ceutrospheres separated, nuclear wall 

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

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

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



niicleole). Such a nucleus is often termed 

 nucleus.^ 



vesicular 



^ 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 mucli confusion 

 in the iise of the terms. 



- For a detailed study of tlie nucleus in Protista, see Calkins in Arch. ProUstcnk. 

 vol. ii. 1903. 



