INTRODUCTION 15 



ity resulting from the interaction. The organism is 

 a mechanism for the storage and transformation 

 of energy, but the source of its energy is the world 

 about it; without frequent replenishment it soon 

 runs down and dies. The idea of a vital principle 

 may be superimposed upon this interpretation but 

 in the present state of our knowledge may not dis- 

 place it; such an idea is, moreover, fatal to a 

 scientific inquiry. 



Obviously the changing world environment 

 which brought about the conditions favorable to 

 the origin of life must, in time, have given rise to 

 other conditions less favorable for its maintenance. 

 The whole history of the world is one of changing 

 climates and geological events which have exposed 

 its various regions to a succession of different con- 

 ditions. The partially independent living sub- 

 stance, if it were to persist through changing en- 

 vironmental conditions, must necessarily have had 

 adequate latitude of response to enable it to meet 

 them, and likewise the environment surrounding 

 an organism could not change beyond the organ- 

 ism's capacity for adjustment without destroying 

 it. These facts still apply to all existing organisms. 



But according to our ideas of evolution the com- 

 plex population of the modern world has evolved 

 from a simple primordium. As the years have 

 passed the living substance has gained tolerance 

 for conditions which would have been fatal to it 



