Appearance and Inheritance of Instincts 201 



probable that it will be formed often again in the same 

 individual, and this repetition will produce a constantly 

 increasing, corresponding modification of the nervous 

 tissue in the individual concerned, which will be repro- 

 duced in his descendants. A new association of ideas 

 can arise and actually does arise independently, within 

 certain limits, of the nervous structure of the individual, 

 and therefore independently of the germ substance also 

 which has produced this latter, in so far as the fortu- 

 itous external circumstances which produce this new 

 association exert a strong and overmastering influence: 

 Among a thousand individuals, quite identical in regard 

 to the structure of their nervous mechanism, this new 

 association of ideas will be developed in only one, on 

 account of the special external circumstances in which 

 it happens to be placed. 



But without the inheritance of acquired characters 

 this fortunate new association of ideas, and the repeated 

 employment of it by the individual later, would be com- 

 pletely lost for the species. To assure its transmission 

 from one generation to another there would remain only 

 imitation or education in the widest sense of the word. 

 But the fact is that nearly all the instincts are, on the 

 contrary, truly inborn, that is to say they are produced 

 without any psychic educative influence whatever. 



It is clear also that not all the members of the older 

 species will be able to make use of a new, fortuitously 

 developed instinct through educative imitation and later 

 through heredity, but only the immediate descendants or 

 associates of the individual in whom it was developed. 

 All other members of the species would be excluded. 

 And so those will be the only ones, who, in consequence 

 of this newly adopted habit, will make a thorough 



