MICRO-ORGANISMS 



old unicellular things vary the least of 

 anything on earth. Mountains may 

 change, but not diatoms nor protozoa. 



III. They were neither created nor 

 modified by their environment, because all 

 conceivable changes of environment have 

 passed over them in their long story with- 

 out ever having made them at all different 

 from what they are now. Some of their 

 species died out, perhaps of pure age, but 

 not from destructive environment, because 

 those forms which still exist are neither 

 their survivors nor successors, but can be 

 found to have been living and multiplying 

 and acting through all the past ages. 



How, therefore, is all this greatest story 

 of physical life to be accounted for? The 

 answer is one which will have to be re- 

 peated more than once as we proceed, 

 namely, that we do not know, nor appar- 

 ently does anybody else know. It is only 

 uninstructed impatience which will assert 

 87 



