124 RESPONSES OF CELLS ON THE BIOLOGICAL LEVEL 



densation upon it of nucleic acid, and a fading away 

 of nucleoli. 



3. Division of the centrosome and breakdown of the 

 nuclear membrane. 



4. Formation of the spindle and of the equatorial plate. 



5. Division of the equatorial plate and movement of 

 chromosomes toward the centrosomes. 



6. Division of the cytoplasm. 



7. Reformation of nuclear membranes. 



8. Despiralisation and loss of nucleic acid from the chro- 

 mosomes, and reconstitution of nucleoli. 

 Obviously mitosis is a very complex process, and if 



mitotic poisons act directly it is obvious that derange- 

 ment will occur at many points, and through interference 

 with many quite distinct phenomena. It is, of course, 

 quite possible that some, if not all, of the known mitotic 

 poisons exercise their effect, not by acting upon the spe- 

 cific processes concerned exclusively in mitosis, but on 

 one or more of the processes which, amongst other 

 things, supply the necessary energy for the different 

 stages of mitosis. 



Among the commoner effects of mitotic poisons are: 



1 . The adhesion of chromosomes to one another (com- 

 monly called "stickiness") and the failure of daughter 

 chromosomes to separate completely from one another. 

 Such phenomena commonly lead to 



2. The breaking of chromosomes, and the formation of 

 chromatin fragments which may not become at- 



