THE EVOLUTION OF MAN 



given conditions. This conception stated in this 

 bare form is startlingly simple. There were 

 enough inorganic substances on this planet, even 

 though in a state of white heat. Whenever a 

 planet cooled, all these substances passed through 

 certain stages of development. Water, for in- 

 stance, then became an inevitable product of evo- 

 lution. Why 'should not life be another product, 

 like water, which developed also at that stage 

 from so-called dead matter? Many very clear 

 and circumspect brains have been satisfied with 

 this simple formulation of the theory of life, and 

 welcomed it as a perfectly rational solution. 

 While in our present historical period life comes 

 only from life so far as we know, it was assumed 

 that in those primitive days the first life rose out 

 of inorganic matter, and this was called "sggn,- 

 taneous generation." And it was generally con- 

 sidered an open question whether such "spon- 

 taneous generation" took place only in the begin- 

 ning, or whether it may have taken place in 

 subsequent ages, occasionally even to-day, along 

 with the normal mode of generation, at least 

 among the very lowest animated beings, though 

 it has never been observed. Now it cannot be 

 denied that this mode of solving the riddle is 

 neither a serious nor a convincing one. It is in- 



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