Active Causes of Organic Evolution 195 



As already indicated for the simple non-nucleate plants, 

 each stimulus and kind of stimulus seems to act separately, 

 and to be separately responded to. iVnd this may in large 

 measure be explained through these organisms living in an 

 environment that during archsean times was relatively monot- 

 onous and unvarying. 



But Tvith advancing evolution of nuclear chromatin or cog- 

 nitic substance, and the correlative incidence during every 

 twenty -four hours of varied stimuli, each organism or part of 

 it acquired an increasing capacity to link together the summated 

 actions of several stimuli, and to project therefrom a response 

 or pathway of action, that was a resultant of all. Examples 

 of such we have cited in the roots and shoots of plants, the 

 movements of infusors, etc. 



The extreme complexity of some proenvironal movements 

 in plants is graphically shown by experimentation with Mimosa 

 or any other amongst hundreds of sensitive species. Each 

 movement also may involve the action, the summated corre- 

 lation, and the organismal reaction, connected "^iv^th four to 

 seven distinct kinds of energizing stimuli. Amongst the higher 

 insects and mammals — where a nervous system with associ- 

 ated cogitic power exists — the rapidity of correlation and 

 response are such that the original separateness of the com- 

 ponent stimuli fails to impress the observer. It is this fact, 

 coupled with a failure to realize the existence in the above 

 animals of a condensed cognitic and cogitic energy, that has 

 hitherto prevented a correct analysis of acts of intelligence, 

 reason, and selection. In the next chapter and also in chapter 

 21 these are more fully discussed. 



(4) Selection. A fourth factor that we believe to be coop- 

 erative with the above three is selection, natural selection, 

 or selective survival. If one watch the life career of an indi- 

 vidual, or the species career of a group of organisms, the im- 

 pression will be gained that, for success or continued existence 

 alike of the one and the other, three requirements have to be 

 fulfilled, viz., successful vegetation, successful defense, and 

 successful reproduction. Under the first of these we include 



