THE GEOLOGIC FUNCTIONS OF LIFE. 651 



be brought under this monopolistic control may not be predicted so 

 easily. 



A similar profound transition in vegetation is being forced by man. 

 The native vegetation is rapidly being replaced by selected varieties, 

 and by varieties that take advantage of conditions furnished by man. 

 As the agricultural control of the earth becomes more complete and 

 effective, a result toward which very rapid progress is bein^ made, a new 

 flora of man's selection will very generally prevail over the whole land 

 surface of the globe. It is doubtful whether at any time in the history 

 of the earth changes of flora and of fauna, and of surface, have been more 

 rapid than those that are now taking place under the accelerating 

 influence of man's action, and this accelerating influence springs not 

 mainly from automatic or instinctive reaction, but from conscious 

 impulse and intelhgent direction. 



(2) The psychological factors as such. — Are the introduction and the 

 evolution of the psychological factors themselves to be regarded as sub- 

 jects of geological study? We shall find that, at the outset, the geologic 

 record is a complete blank so far as clear evidence of terrestrial organisms 

 actuated by their own intelhgence is concerned ; that later, organisms 

 with some apparent consciousness and intelligence appeared, and that 

 the mental element increased apace unto its present attainment. We 

 know that relationships of a sociological nature arose in apparent feeble- 

 ness, and gradually evolved into more definite, higher, and more com- 

 plex forms. By sociological factors we mean merely those conscious 

 relations which one organism bears to another, of which the parental 

 and the gregarious impulses are two fundamental expressions. For 

 manifest reasons, the introduction and evolution of the psychological 

 and sociological factors themselves have received little direct recogni- 

 tion as a portion of geological studies. The record of such factors in 

 the fossils of past ages is necessarily obscure and imperfect, and the 

 interpretation of what there is lacks certainty and precision. None 

 the less, this psychological record, with all its imperfections, is beyond 

 valuation, and must, we think, come to be an indispensable factor in 

 the study of psychological and sociological evolution, for it shows, what 

 nothing else can show equally well, the extremely prolonged history 

 of that evolution, and it gives hints of modes and means which no study 

 of existing stages can equally reveal. The organization of the Cam- 

 brian trilobites, for example, implies no small development of the senses 



