MITOTIC POISONS 125 



tached to the spindle at subsequent divisions. These 

 phenomena lead to unequal distribution of chromatin 

 between daughter cells. 



3. Failure of spindle formation. This may lead to poly- 

 ploidy, and on occasion, if the chromosomes have 

 failed to aggregate, to the formation of micronuclei, 

 each organised by one or a small group of chromo- 

 somes. 



4. The formation of multi-polar spindles, perhaps due to 

 multiple division of the centrosome, or perhaps to the 

 formation of new centrosomes. The usual result of 

 this process is the uneven partition of chromatin be- 

 tween daughter cells, or occasionally the formation 

 of a multinucleate cell. 



5. Chromosomes adhesions may prevent the complete 

 separation of the nuclei, and the result may be that 

 cell division does not go to completion. 



6. All the processes through which the spindle goes may 

 be slowed down. 



7. Over-spiralisation, and failure to despiralise after cell 

 division, may occur. 



8. As a result of fragmentation and breaking, transloca- 

 tion may occur. 



9. Cell division may fail to go to completion, resulting in 

 the formation of a bi- or multinucleate cell. 



In view of the complexity of the phenomena involved 

 in mitosis and the great variety of abnormalities which 

 may occur, it is obviously insufficient to classify drugs 



