14 THE MECHANISTIC THEORY OF LIFE 



inorganic world. Here the genius of Charles 

 Darwin has provided an explanation in har 

 mony with the mechanistic theory. No type 

 of organism can survive in which the physio 

 logical mechanisms are not so constituted and 

 so co-ordinated that the organism is capable 

 of completing a life-cycle culminating in 

 the transmission of a similar structure to its 

 descendants. Those organisms and their de 

 scendants which have varied in structure in a 

 direction which gives them a smaller proba 

 bility of surviving will become extinct in the 

 fierce struggle for existence which prevails 

 everywhere among living organisms. On the 

 other hand, those which have varied in such 

 direction as to give them a greater proba- 

 ility of surviving will increase and multiply, 

 isplacing the inferior types. Hence by the 

 lind operation of natural selection through 

 ountless ages higher and higher types of 

 rganism will be produced. 



The wonderful complexity, accuracy, and 

 co-ordination of the physiological mechanisms 

 found within the bodies of living organisms 

 can thus be accounted for on purely mechani 

 cal principles. All that it is necessary to 



