MICRO-ORGANISMS 



could be best investigated in that great 

 division of the living kingdom which is 

 composed wholly of unicellular organisms, 

 or living things which have but one cell to 

 their physical being. This apparently 

 would make our problem quite simple, for 

 as there are no complex relations with other 

 things to interfere, we have but one living 

 thing before us which lives, reproduces it- 

 self, and dies the same small, single, uni- 

 cellular entity throughout. Moreover, 

 these things are universally rated as the 

 lowest and simplest forms of life and 

 therefore possibly not far removed from 

 the inorganic kingdom. 



,But the more we learn about the unicel- 

 lular world of life, the more unthinkable 

 abiogenesis becomes. 



In the first place, unicellular forms dif- 

 fer widely, and yet so definitely between 

 themselves that they can be divided into 

 four distinct genera. First come the 

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