14 THE PROBLEMS OF EVOLUTION 



to modern concepts, probably resulted from the 

 proper association of inorganic materials at a re- 

 mote period in the history of the world when a pecu- 

 liar complex of conditions prevailed, this primordial 

 living material was evidently a product of in- 

 organic factors entirely. In other words, if the 

 idea is valid that life had a beginning, barring the 

 doctrine of special creation and vitalistic theories, 

 it must have been a product of things which we 

 now recognize as factors in its environment. 



In order to fall within the category of living 

 things, this substance must necessarily have had 

 some capacity to maintain and reproduce itself, 

 the former ability including a simple expression of 

 the various phenomena of adaptation and metabo- 

 lism. Maintenance and reproduction need not have 

 been more than a complex form of autocatalysis. 

 Thus the origin of a partially independent sub- 

 stance as a product of non-living factors entirely 

 is not difficult to conceive. With its origin, the 

 activity of living things began, consisting of an 

 interaction between the living substance and its 

 surroundings. Since then we have a source in liv- 

 ing matter to consider as well as the inorganic fac- 

 tors associated with its existence, for the spon- 

 taneous origin of life has not been demonstrated 

 and most living things have probably arisen from 

 a single ultimate source. Life itself, so far as we 

 have been able to determine, is the manifest activ- 



