CHAPTER IX. THE ENERGY OF 

 EVOLUTION. 



IF we view the phenomena of organic life from the 

 standpoint of the physicist, the first question that 

 naturally arises in the mind is as to the kind of energy 

 of which it is an exhibition. Ordinary observation 

 shows that organic bodies perform molar movements, 

 and that many of them give out heat. A smaller num- 

 ber exhibit emanations of light and electricity. Very 

 little consideration is sufficient to show that they in- 

 clude among their functions chemical reactions, a con- 

 viction which is abundantly sustained by researches 

 into the physiology of both animals and plants. The 

 phenomena of growth are also evidently exhibitions of 

 energy. The term energy is used to express the mo- 

 tion of matter, and the building of an embryo to ma- 

 turity is evidently accomplished by the movement of 

 matter in certain definite directions. The energy which 

 accomplishes this feat is, however, none of those which 

 characterize inorganic matter, some of which have just 

 been mentioned, but, judging from its phenomena, is 

 of a widely different character. If we further take a 

 broad view of the general process of progressive evo- 

 lution, which is accomplished by successive modifica- 

 tions of this growth-energy, we see further reason for 



