5 1 6 PRIMAR Y FA C TORS OF OR GANIC E VOL UTION. 



mized in the following language : ' Evolution of living 

 types is then a succession of elevation of platforms, 

 on which succeeding ones have built. The history of 

 one horizon of life is that its own completion but pre- 

 pares the way for a higher one, furnishing the latter 

 with conditions of a still further development. Thus 

 the vegetable kingdom died, so to speak, that the ani- 

 mal kingdom might live, having descended from an ani- 

 mal stage to subserve the function of food for animals. 

 The successive types of animals first stimulated the 

 development of the most susceptible to the conflict, 

 in the struggle for existence, and afterwards furnished 

 them with food.' In the occupation of the world's 

 fields, the easiest and nearest at hand have been first 

 occupied, and successively those which were more dif- 

 ficult. The digging animals are generally those which 

 first abandoned the open field to more courageous or 

 stronger rivals ; and they remain to this day generally 

 of low type compared with others of their classes (e. g. 

 Monotremata, Glires, Insectivord]. All occupations have 

 been filled before that one which requires the greatest 

 expenditure of energy, i. e. mental activity. But all 

 other modes of life have fallen short of this one in giv- 

 ing the supremacy over nature." 



We now approach an explanation of the phenome- 

 non of anagenesis. Why should evolution be pro- 

 gressive in the face of universal catagenesis? No other 

 ground seems discoverable but the presence of sensa- 

 tion or consciousness, which is, metaphysically speak- 

 ing, the protoplasm of mind. The two sensations of 

 hunger and sex, have furnished the stimuli to internal 

 and external activity, and memory, or experience with 

 natural selection, have been the guides. Mind and 

 body have thus developed contemporaneously and 



