in.] THE MEANING OF EVOLUTION 255 



that we behold in nature. Hence a discord, striking 

 and terrible, but for which the original principle of life 

 must not be held responsible. 



The part played by contingency in evolution is there- 

 fore great. Contingent, generally, are the forms adopted, 

 or rather invented. Contingent, relative to the obstacles 

 encountered in a given place and at a given moment, 

 is the dissociation of the primordial tendency into such and 

 such complementary tendencies which create divergent 

 lines of evolution. Contingent the arrests and set-backs; 

 contingent, in large measure, the adaptations. Two 

 things only are necessary: (1) a gradual accumulation 

 of energy; (2) an elastic canalization of this energy in 

 variable and indeterminable directions, at the end of which 

 are free acts. 



This twofold result has been obtained in a particular 

 way on our planet. But it might have been obtained 

 by entirely different means. It was not necessary that 

 life should fix its choice mainly upon the carbon of car- 

 bonic acid. What was essential for it was to store solar 

 energy; but, instead of asking the sun to separate, for 

 instance, atoms of oxygen and carbon, it might (theoret- 

 ically at least, and, apart from practical difficulties possibly 

 insurmountable) have put forth other chemical elements, 

 which would then have had to be associated or dissociated 

 by entirely different physical means. And if the element 

 characteristic of the substances that supply energy to the 

 organism had been other than carbon, the element char- 

 acteristic of the plastic substances would probably have 

 been other than nitrogen, and the chemistry of living bodies 

 would then have been radically different from what it is. 

 The result would have been living forms without any 

 analogy to those we know, whose anatomy would have 

 been different, whose physiology also would have been 



