LIFE AS MECHANISM 



discovered, many extraordinary processes have been 

 followed, but so far as one can see, after unravelling 

 the confused ideas and technical language of the bi- 

 ologists, we can say hardly anything more than that 

 the cell increases in size and divides into two parts, 

 and that the chromosomes within the cell also grow 

 and split. The dividing continues until after a while 

 we notice that some of the aggregates of cells differ 

 from other aggregates, and from the various different 

 aggregates, the different parts and organs begin to 

 show their characteristic attributes. At this stage the 

 mass is called an embryo; it is followed by birth, 

 growth to maturity, decay, and death. As the funda- 

 mental axiom of biology, we shall accept the belief 

 that no cell occurs except from the growth and di- 

 vision of a former cell; in spite of this we are also 

 asked to accept the axiom of evolution that the cell 

 has evolved ultimately from purely material ele- 

 ments. 



It would hardly be an exaggeration to say that the 

 study of the cell is the science of biology. Schleiden 

 started the domination of the cell by the dictum that : 

 "In the strictest sense of the word, only the separate 

 cell deserves to be called an individual.""^ And most 

 biologists would probably subscribe to this doctrine. 

 A man, a dog, or a tree, is not an individual, an or- 

 ganism, but each is an aggregation of cells, and to 

 know what we call the individual it is necessary to 



25 Schleiden, Contribution to Phytogenesis. 



1:2833 



