INTRODUCTION Xlll 



cant amount of space in the scientific literature of the world. 

 Now, however, large numbers of books, articles, reviews and 

 exj>erimental papers are already being devoted to it. To-day 

 we are not satisfied by any merely speculative interpretation 

 of the history of the phenomena which have occurred at some 

 time or another on our planet. We must check our knowledge 

 by experiment. We must reproduce experimentally the 

 separate stages in the historical development of matter and 

 finally create life again, synthetically, not by the long and 

 devious route by which this synthesis took place in nature, 

 but by a route based on a thorough understanding of those 

 forms of organisation which we find already in a finished 

 state in existing living things. 



This task is certainly exceptionally complicated but con- 

 temporary science has indications upon which it can, at least, 

 make an estimate of the work in real terms. 



In what follows I shall do my best to make clear the ways 

 in which human minds have tried to solve the problem of 

 the origin of life. I shall give a short account of the numerous 

 doctrines and theories which have been formed during many 

 centuries, but I shall devote the greater part of my attention 

 to drawing a picture of the progressive development of matter 

 which, in my opinion, led up to the emergence of life on 

 our planet. 



