CELL DIVISION AND HEREDITY 



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 ex- 

 ternal forces. 



It has been suggested that cell division might be 

 due to the fact that as an object grows larger 

 there will be a point reached where it will become 

 physically unstable, due to the fact that its mass, 

 which contributes to its instability, increases as 

 the third power of its linear dimensions, whereas 

 its surface, which by reason of its surface tension 

 contributes to its stability, increases only as the 

 second power of its linear dimensions. Such an 

 explanation is inadequate because the mere pres- 

 ence of a large mass or volume would not cause an 

 object to divide into fragments unless it be acted 



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