HOW LIFE CAME TO EARTH 171 



a discovery made, it will be observed, in 

 studying the question of the origin of life. 

 Vast industries concerned in the preparation 

 and preservation of food, and in the scientific 

 fertilization of land, are also based on this 

 unique discovery. 



Yet all this by no means settles in the 

 negative the question of the spontaneous 

 origin of life, it only proves clearly that life 

 cannot arise under a particular set of con- 

 ditions, and so narrows the issue and leads 

 onward to new experimental questions which 

 may even be as fruitful as the old ones. 



CHAPTER VIII 



HOW LIFE CAME TO EARTH 



When it became settled that life did not arise 

 spontaneously on the earth, in the particular 

 way that had been supposed from dead organic 

 matter, the minds of scientists turned towards 

 the explanation of the course by which it 

 had made its advent upon our planet from 

 elsewhere. 



One hypothesis which appears to have 

 sprung up spontaneously in many minds, 



