THE ENERGY OF EVOLUTION. 481 



is obedient. Thus the successive stages of embryonic 

 growth are limited in number in each species. The 

 dimensions of most species are limited within a def- 

 inite range. The duration of life, or of the functioning 

 organic machine, has a definite limit in time. All this 

 means that a certain limited quantity of energy is at 

 the disposal of each individual organism. 



In the preceding pages I have endeavored to show 

 what causes have been and are efficient in the produc- 

 tion of different types of organic life, through the 

 modifications of the bathmic energy. We will now 

 briefly consider the question of the origin of the living 

 substance, protoplasm or sarcode, which exhibits bath- 

 mism. 



On this subject Professor Manly Miles remarks : l 

 "Omitting subordinate details, which represent the 

 separate links in the chain of events, the processes of 

 nutrition may be summarized in general terms as fol- 

 lows : In plants the chemical elements and binary com- 

 pound on which they feed, are built up by successive 

 steps of increasing complexity and instability into pro- 

 toplasm, with a storing of the energy made use of in 

 the constructive process, which is derived from the 

 heat and light of the sun. The constructive processes 

 are expressed by the term anabolism, and the products 

 of the different upward steps are called anastatic. Pro- 

 toplasm, the most complex and unstable of organic 

 substances, is the summit of the ascending steps of 

 anabolism ; and katabolism, which represents the suc- 

 ceeding downward steps of metabolism, then follows, 

 and its products or katastates are starch, cellulose, 

 proteids, etc., or what we recognize as the proximate 



1 Proceeds. Amer Assoc. Adi'. Set., 1892, p. 203. 



