142 ORGANIC EVOLUTION — MENTAL 



events too numerous and heterogeneous to be provided 

 against by an unvarying machinery. 



The entire passage from reflex action in its lowest 

 manifestations, to reason in its highest manifestations, is 

 therefore a process of increasing adaption to environ- 

 ments increasing in complexity. Low in the animal 

 scale a few heterogeneous structures and reflexes provide 

 ao-ainst the few heteroaeneous events that occur in the 

 simple environment. Higher in scale the greater hete- 

 rogeneity of the events to be provided against is met 

 by the evolution, through Natural Selection, of a greater 

 number of heterogeneous structures and reflexes. Higher 

 still, when the environment becomes yet more complex, 

 reflex action is supplemented by instinct, which, though 

 undeviating in its promptings, is associated with con- 

 sciousness and controlled to some extent by volition, 

 whereby the element of choice is introduced, and the 

 adaptability of the organism to its environment vastly 

 increased. Highest of all, increasing still more the 

 adaptability, when the events in the environment to be 

 provided against have become so heterogeneous and 

 multitudinous that by no evolution of new physical 

 structures, accompanied by new reflexes and instincts, 

 can they be provided against, there occurs that j)hysical 

 variability, in adaption to circumstances, to which I 

 have so persistently called attention, and that ac- 

 companying mental variability on which I as strongly 

 insist, and which we call reason. 



Now there is no vestige of proof that instincts are 

 increased by stimulation, i. e. that they are not only 

 called into activity by stimulation, but are sharpened 

 by it. Indeed, if our definitions are correct, such a 

 supposition involves a contradiction in terms, since what- 

 ever is mentally acquired pertains to reason, nut to 

 instinct. Again, it is obvious that reason is not trans- 

 missible, since in each generation it must be acquired 



