THE ENERGY OF EVOLUTION. 475 



the variation should appear in a large number of indi- 

 viduals coincidentally and successively. It is exceed- 

 ingly probable that that is what has occurred in past 

 geologic ages. We are thus led to look for a cause 

 which affects equally many individuals at the same 

 time, and continuously. Such causes are found in the 

 changing physical conditions that have succeeded each 

 other in the past history of our planet, and the changes 

 of organic function necessarily produced thereby. 



I. ANAGENESIS. 



It is customary to distinguish, broadly between in- 

 organic and organic energies, as those which are dis- 

 played by non-living and living bodies. This classifi- 

 cation is inexact, since, as already remarked, nearly 

 all of the inorganic energies are exhibited by living 

 beings. A division which appears to be, with our 

 present knowledge, much more fundamental, is into 

 the energies which tend away from, and those' which 

 tend toward, the phenomena of life. In other words, 

 those which are not necessarily phenomena of life, and 

 those which are necessarily such. And the phenom- 

 ena of life here referred to are the phenomena of growth 

 and evolution, as distinguished from all others. I have 

 termed ^ these classes the Anagenetic, which are ex- 

 clusively vital, and the Catagenetic, which are phys- 

 ical and chemical. The anagenetic class tends to up- 

 ward progress in the organic sense ; that is, toward 

 the increasing control of its environment by the organ- 

 ism, and toward the progressive development of con- 

 sciousness and mind. The catagenetic energies tend 

 to the creation of a stable equilibrium of matter, in 



1 The Monist, Chicago, 1893, p. 630. 



