208 Causes and Course of Organic Evolution 



in the minds of their inceptors as concrete mentally visible 

 pictures, that lived for them as truly as though they had been 

 already finished and visible to the naked eye. In each case, 

 as a result of many previous isolated stimuli of a lumic, a 

 mechanic, a gravic, a chemic nature, that had gradually been 

 summated into an energizing whole, there was formed in the 

 inceptor's mind a resultant proenvironal response of a highly 

 complex character, that enabled each structure truly to stand 

 forth in mental perspective, when as yet no material indication 

 of it existed. This brought into play all those higher phe- 

 nomena of living cells that we designate as memory, reflection, 

 intelligence, constructiveness, and so on. 



So, by the exercise primarily of a wide series of distinct sense 

 impressions, several summated proenvironal responses origi- 

 nated. These again were compounded by cells of the highest 

 brain centers into complex resultant responses, and gave rise 

 there to the mental picture that slowly projected itself in 

 marble as the classic cathedral, or in metal as the elaborate 

 printing machine. 



But by selecting an example here and there, along the entire 

 scale of caryotic or nucleate life, we hope to show that, from 

 the simplest to the most complex, the proenvironal law is 

 constantly at play, and in fact is a fundamental law of all 

 nucleated cells. 



The origin of it is to be sought for, in those primitive re- 

 sponses of living substance that caused such constantly to 

 grow or move toward a position or region that would prove 

 viost satisfying to the organized molecules, when these were 

 acted on by thermic, lumic, gravic, chemic, or electric stimuli. 

 This again carries us backward to the more primitive inorganic 

 relation of "satisfied" or "unsatisfied" molecules or atoms, 

 in connection with other chemical or chemico-physical con- 

 ditions, as has been so often and ably urged by J. Loeb. 



Thus one of the simplest and most delicate exhibitions of 

 it consists in the movements of aerobic bacteria to centers 

 where oxygen sui)i)]y is amply sufficient to their needs, as 

 demonstrated by Engelmann. In this case the presence of 



