Growth and Movement. 



109 



Fig. 46. 



Diagrammatic representation of Nuclear and Cell Division. 



1. A cell with resting nucleus just previous to division. The cytoplasm (stippled) 

 fills the cell cavity. The nuclear thread is shown as a tortuous band throughout the 

 nucleus ; the black body in the nucleus is the nucleolus. 



2. The nuclear membrane and the nucleolus have disappeared, the nuclear 

 thread has become divided transversely into distinct bodies termed chromosomes, 

 and these are seen to be divided longitudinally. 



3. The chromosomes have become lined up at the equator of the cell and pro- 

 toplasmic threads converge from them toward opposite poles. 



4. The same as 3 seen from one of the poles. 



5. The longitudinal halves of the chromosomes are moving toward opposite 

 poles. 



6. A later stage, showing connecting protoplasmic threads between the receding 

 chromosomes. 



7. The chromosomes arrived at the opposite poles are fusing together end to 

 end to form nuclear threads. 



8. The nuclear threads have assumed the form of two daughter nuclei, nucleoli 

 have appeared, the connecting threads have spread from wall to wall, and a new 

 cell wall dividing the mother cell in halves is being formed, apparently by the con- 

 necting threads. 



9. A nuclear membrane has been formed about the daughter nuclei, the con- 

 necting threads have disappeared, and nuclear and cell division is completed. 



