48o PRIMARY FACTORS OF ORGANIC EVOLUTION. 



plest exhibition is the subdivision of a unicellular pro- 

 toplasmic body into two or more individuals or struc- 

 tural units of a multicellular organism. Further divi- 

 sion of the latter does not abolish the individual, but 

 extends it, and we now observe the elaboration of dif- 

 ferent structural types to become the conspicuous func- 

 tion of this form of energy. In other words, a once 

 simple energy becomes specialized into specific ener- 

 gies, each of which, once established, pursues its mode 

 of motion in opposition to all other modes not more 

 potent than itself. Besides the evident truth of the 

 proposition that a mode of building is a mode of mo- 

 tion, we have another very good reason for believing 

 in the existence of a class of bathmic or growth-ener- 

 gies. This is found in the phenomena of heredity. 

 The most rational conception of this inheritance of 

 structural characters is the transmission of a mode of 

 motion from the soma to the germ-cells. This is a far 

 more conceivable method than that of the transmis- 

 sion of particles of matter, other than the ordinary ma- 

 terial of nutrition. The bathmic theory of heredity 

 bears about the same relation to a theory of transmis- 

 sion of the pangenes of Darwin, or the ids of Weis- 

 mann, as the undulatory theory of light and other 

 forms of radiant energy does to the molecular theory 

 of Newton. I have therefore assumed as a working 

 hypothesis the existence of the bathmic energy, and 

 have inquired how far the facts in our possession sus- 

 tain it. In doing so it has been necessary to elaborate 

 the theory so as to render clearer its application to spe- 

 cific cases. The fact to be accounted for is its spe- 

 cialization into so many diverse specific forms. 



A further indication of the existence of the bathmic 

 energy is the quantitative limitation to which growth 



