176 ORGANIC EVOLUTION — MENTAL 



often nothing luoro tlian mere extensions of their 

 instincts. Thus the cat and tlie tiger instinctively 

 know how to hunt their prey, but they do it better for 

 the instructions given them by their progenitors. 

 Young birds know how to build nests, but evidently 

 learn by experience, since older birds are the better 

 architects. Such traits as these, which are easily ac- 

 quired, can have been little improved on since they were 

 first superimposed on instinct. But such traits as 

 language in man, and probably also many traits in ants, 

 which are acquired with difficulty by the individual, 

 the acquirement of which occupies a considerable time 

 during the ontogeny, and which considerably supple- 

 ment such instincts as the animal possesses, must have 

 arisen only by small accretions, slowly and painfully 

 added during the phylogeny. They are found only in 

 mentally the highest animals, and betoken in them 

 great powers of varying mentally in response to stimula- 

 tion, of acquiring reason. Every such trait is one which 

 considerably increases the harmony with the environ- 

 ment, and is one therefore which very favourably in- 

 fluences the survival rate; as is easily proved a pos- 

 teriori, and of which a irriori proof is furnished by the 

 fact, that notwithstanding the time spent and the 

 mental toil endured by each individual in acquiring it, 

 it yet remains persistent in the species. 



Savage man differs from lower animals chiefly in that 

 he possesses the power of acquiring articulate speech, 

 and the knowledge he thereby acquires enables him 

 to place himself in harmony with an environment of 

 far greater complexity than that of any other animal. 

 Civilized man differs from savage man chiefly in that he 

 has invented, and more or less perfected, certain artificial 

 aids to speech, by virtue of which he is enabled to ac- 

 quire or store in an available shape vastly more know- 

 ledge than the savage, and is therefore able to adapt 



