42 Spirazines 



forces, and it has never been shown that physical 

 disturbance is necessary for cell division. 



Cell division cannot be attributed to surface 

 tension because the eifect of surface tension is 

 always to hold a body together and never to sepa- 

 rate it into fragments, but even if surface tension 

 would act in the opposite direction from that in 

 which it actually does act it would still be insuf- 

 ficient to account for cell division because the 

 cohesive strength of protoplasmic fibers is far 

 greater than any force that could possibly result 

 from surface tension. 



Another suggestion has been that cell division 

 might be due to the fact that as an organism be- 

 comes larger its food requirements increase with 

 the third power of its linear dimensions whereas 

 the quantity of food within reach increases only 

 as the first or second power. This explanation is 

 also inadequate because shortage of food would 

 only cause an organism to become under-nour- 

 ished, which might retard its growth and eventu- 

 ally result in its death, but would not cause it to 

 divide. Attempts to explain cell division on the 

 basis of food economy have been due to a confu- 

 sion of the principles of phylogeny with the prin- 

 ciples of ontology. 



Numerous other hypotheses have been pro- 

 posed, but they have all been found untenable for 



