INTRODUCTION 11 



likewise complex association of conditions. This 

 is true even of intelligent man with his relatively- 

 great power to control the conditions of his own 

 life. 



It must be admitted that the physico-chemical 

 basis has not yet been proved the sole explanation 

 of life, but we may confidently predict that it is a 

 universal foundation for the manifestation of life. 

 Vital processes have never yet been demonstrated 

 independently of such a foundation and, until they 

 are, the problems of evolution should be susceptible 

 of solution to the same extent as most of our prob- 

 lems of science. When we explain a natural phe- 

 nomenon, we have merely resolved it into its com- 

 ponent simpler phenomena; we push back the 

 barriers of ignorance but never wholly remove 

 them. In the case of evolution we first had to 

 recognize its occurrence. Then it was necessary 

 to bolster it up with adequate evidence in the vari- 

 ous fields of science. And all the while we have 

 been struggling to learn how it proceeds, but here 

 our footing crumbles and long before we get to 

 why, we have such a difficult task on hand that we 

 are still struggling. The problem of life itself is 

 very near this why. Given life, be it the result of 

 an elan vital, a Z-system, or merely of a peculiarly 

 intricate physico-chemical organization, we have 

 a satisfactory foundation for the investigation of 

 the how of evolution. 



