often nothing more than mere extensions of their instincts. Thus the cat and the 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 acquired, 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 supplement 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 stimulation, of acquiring reason. Every such trait is one which considerably increases the harmony with the environment, and is one therefore which very favourably influences the survival rate; as is easily proved à posteriori, and of which à priori 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 acquire or store in an available shape vastly more knowledge than the savage, and is therefore able to adapt
