282 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



increasing complexity, sustained through the interchange of energy. 

 Darwin's principle of the survival or elimination of various forms of 

 living energy is, in fact, adumbrated in the survival or elimination of 

 various forms of lifeless energy as witnessed among the stars and 

 planets. In other words, Darwin's principle operates as one of the 

 causes of evolution in making the lifeless and living worlds what they 

 now appear to be, but not as one of the energies of evolution. Selec- 

 tion merely determines which one of a combination of energies shall 

 survive and which shall perish. 



The complex of four interrelated sets of physicochemical energies 

 which I have previously set forth as the most fundamental biologic 

 scheme or principle of development may now be restated as follows: 



In each organism the phenomena of life represent the action, reaction, 

 and interaction of four complexes of physicochemical energy, namely, 

 those of (i) the Inorganic Environment, (2) the developing Organism 

 (protoplasm and body-chromatin\ (3) the germ or Heredity-Chromatin, 

 (4) the Life Environment. Upon the resultant actions, reactions, and 

 interactions of potential and kinetic energy in each organism Selection 

 is constantly operating wherever there is competition with the correspond- 

 ing actions, reactions, and interactions of other organisms. 



This principle I shall put forth in different aspects as the central 

 thought of these lectures, stating at the outset and often recurring 

 to the admission that it involves several unknown principles and 

 especially the largely hypothetical question whether there is a relation 

 between the action, reaction, and interaction of the internal energies 

 of the germ or heredity-chromatin with the external energies of the 

 inorganic environment, of the developing organism, and of its life 

 environment. In other words, while this is a principle which largely 

 governs the Organism, 'it remains to be discovered whether it also 

 governs the causes of the Evolution of the Germ. 



As observed in the preface we are studying not one but four 

 simultaneous evolutions. Each of these evolutions appears to be 

 almost infinite in itself as soon as we can examine it in detail, but of 

 the four that of the germ or heredity-chromatin so far surpasses all 

 the others in complexity that it appears to us infinite. 



The physicochemical relations between these four evolutions, 

 including the activities of the single and of the multiplying organisms 

 of the Life Environment, may be expressed in diagrammatic form as 

 follows : 



