EVOLUTION AND ITS CONSEQUENCES. 39 



De the location of activity in the brain, that its stages of growth 

 would be the principal changes of structure to be witnessed in 

 human history, together with those which should result from loss 

 of growth-force in other regions by abstraction. 



To return to the material aspect of the case. The discrimina- 

 tion between pleasure and pain locates motive-force, which is 

 derived from without. Motion or use locates growth-force, also 

 derived from without, and thus produces organs out of material 

 derived from without. These organs diversify the directions of 

 motion. From new movements arise new pleasures and pains, 

 and motion is again "located" in its exhibitions in some particu- 

 lar directions, and restrained in others. These directions depend 

 on external circumstances at the first. The determination of 

 motion to certain lines locates growth-force in those lines, and 

 new parts are produced, which are further executive organs and 

 types of structure. We now repeat the circuit. New executive 

 organs introduce new contiguities, the number depending on the 

 general complication of the animal in connection with that of the 

 organ, and new pleasures and pains result. The pleasures again 

 determine activity, and, under the circumstances already men- 

 tioned, growth-force is again located. 



In these facts lies the explanation of the principle of direction 

 or location of executive structures about the head, termed by 

 Prof. Dana "cephalization." The increasing demands of in- 

 telligence locate growth-force round its organ, the brain, etc., 

 while such location reacts by furnishing means of increased ac- 

 tivity of mind. 



These conjunctions of growth with executive capacity, consti- 

 tute a class of "expression points"; points attained without 

 leaps, and abandoned without abruptness, but constituting great 

 steps of i^rogress, pregnant with future results. 



The part played by "intelligent selection" remains to be 

 considered. I have heretofore spoken only of variation of types, 

 and not dwelt on their persistence. This is a most important 

 consideration, for most men see a great deal more of tlie latter 

 than the former. Species present their characters intact for long 

 periods, and many structural peculiarities have had great range 

 in time. 



I recur to the origin of the "location of growth-force," i. e., 

 the direction of motive-force. This is located by the appreciation 

 of pleasure and pain. Now, every one knows that different ani- 



