234 THE PRINCIPLES OF HEREDITY 



world is only to a small extent inborn and instinctive. He 

 inherits comparatively little of that sort from his parent, and 

 transmits little of the kind to his child. But he is pre- 

 eminently capable of learning. Though his mind is almost a 

 blank at birth, yet every sight and sound, every sensation 

 and experience, adds to the store of knowledge piled up in 

 his immense memory. One frog is mentally almost similar 

 to any other frog. Under given conditions all frogs act 

 much alike. They move in a narrow instinctive groove. 

 But because man depends so greatly on experience, and 

 since the experiences of different men may differ very widely, 

 it follows that men may differ very greatly in mind from 

 one another. Under given circumstances men who have not 

 had the same training do not act in the same way. Their 

 actions are controlled by their acquirements; they do not 

 move in a narrow instinctive groove. One man acquires 

 Spanish, another English; one man becomes a hunter, 

 another a statesman ; one becomes a priest, another studies 

 science ; one is civilized, another is savage. The differences 

 are endless. 



some notion, however small, of the past, and some conception, however 

 confused, of the future. 



As I greet my old school-master in my dreams, so, presumably, does 

 a frog greet a snake or a rival. If a fly that he was about to eat were 

 turned into a snake about to eat him, he would feel alarm doubtless, 

 but probably no surprise. It is true, of course, that I really got my 

 knowledge of my school-master through experience, and that in this 

 I differ from the frog, who gets his knowledge of the snake through 

 instinct. But in my dreams my acquired knowledge seems to take on 

 the type of instinct. It appears innate, as if the physical characters in 

 my brain, with which it is correlated, had developed otherwise than 

 through use and experience ; as if they had developed as Adam's navel 

 is said by theologians to have developed. 



