THE CAUSE OF CELL DIVISION 

 Every living organism exhibits during some 

 period of its existence the phenomenon of cell 

 division, which may take place either by simple 

 fission as in the case of bacteria, by budding as in 

 the case of yeasts, by direct amitotic division of 

 the nucleus as in the case of pathological growths 

 or tissues of a transcient nature, or by mitotic 

 division of the chromosomes either with or with- 

 out the formation of centrosomes and asters as in 

 the case of nearly all higher plants and animals. 

 The process is always entirely spontaneous, so 

 that it must be the result of internal and not of 

 external forces. 



It has been suggested that cell division might 

 be due to the fact that as an organism grows 

 larger there will be a point reached where it will 

 become physically unstable, due to the fact that 

 its mass, Avhich contributes to its instability, in- 

 creases as the third power of its linear dimen- 

 sions, whereas its surface, which by reason of its 

 surface tension contributes to its stability, in- 

 creases only as the second power of its linear 

 dimensions. Such an explanation is inadequate 

 because the mere presence of a large mass or 

 volume would not cause an object to divide into 

 fragments unless it be acted upon by external 



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