i8 THE ORIGIN AND EVOLUTION OF LIFE 



protected from capture or invasion by other organisms. Finally, 

 there is the most mysterious and comprehensive process of all, 

 by which aU these manifold modes of energy are reproduced in 

 another organism. The evolution of these complex modes of 

 action, reaction, and interaction is traced through all the early 

 chapters of this volume and is summed up in Chapter V (p. 

 152) as a physicochemical introduction to the evolution of ver- 

 tebrate form. 



The Four Coivjplexes of Energy 



The theoretic evolution of the four complexes is somewhat 

 as follows: 



(i) In the order of time the Inorganic Environment comes 

 first; energy and matter are first seen in the sun, in the earth, 

 in the air, and in the water — each a very wonderful complex 

 of energies in itself. They form, nevertheless, an entirely 

 orderly system, held together by gravitation, moving under 

 Newton's laws of motion, subject to the more newly discovered 

 laws of thermodynamics. In this complex we observe actions 

 and reactions, the sum of the taking in and the giving out of 

 energy, the conservation of energy. We also observe inter- 

 actions wherein the energy released at certain points may be 

 greater than the energy received, which is merely a stimulus for 

 the beginning of the local energy transformations. This energy 

 is distributed among the eighty or more chemical elements of 

 the sun and other stars. These elements are combined in plants 

 into complex substances, generally with a storage of energy. 

 Such substances are disintegrated into simple substances in ani- 

 mals, generally with a release of energy. All these processes 

 are termed by us physicochemical. 



