44 Darwinism and Other Essays. 



tions are formed after birth under the influence 

 of outward circumstances which slightly vary 

 from generation to generation. Where there is 

 no infancy, all the most important nervous com 

 binations are established before birth, and under 

 the unmodified influence of the powerful conserva 

 tive tendency of heredity. Where there is an in 

 fancy, many important nervous combinations are 

 not formed until after birth, and the strictly con 

 servative tendency of heredity is liable to be 

 modified by the fact that the experience of the 

 offspring amid environing circumstances is not 

 likely to be precisely the same as that of the par 

 ent. The prolongation of infancy, therefore, in 

 creases the opportunities for the production of a 

 mental type more plastic than that which is wit 

 nessed in the lower animals ; it paves the way for 

 inventiveness and for progress. It is, further 

 more, the increased variety of experience result 

 ing from this increased mental plasticity that leads 

 to the power of abstraction and generalization 

 the power of marking out and isolating in thought 

 the element that is common to different groups of 

 phenomena. 



Now, in the first employment of articulated 

 words by inchoate man, who had hitherto only 

 grunted or howled, the main point to be inter 



