distinction between instinct and all other psychological 

 phenomena, and if we remember that instincts appear as 

 perfectly developed in those animals possessing them from 

 the moment of their birth, whereas intelligence represents 

 the aggregate of successive experiences ; that the one is 

 almost immutable and stationary, whilst the other is variable 

 and progressive we shall at any rate be able to distinguish 

 between the two sets of phenomena. Beyond all doubt, 

 however, instincts, however defined, are hereditarily trans- 

 missible, as the psychical as well as the physical nature are 

 unquestionably transmitted from parents to their children. 

 As surely as the entire range of animal life up to man 

 himself is possessed of, and actuated by, instincts, so surely 

 is this immense range subjected to the laws of heredity, 

 and this fact is so self-evident as to be universally recognised 

 and admitted. I have just said that instincts are almost 

 immutable, but they are not quite invariable, as the action 

 of external circumstances and domestication tend to modify 

 them to some extent ; and, as showing the potency of 

 heredity, even these acquired modifications are undoubtedly 

 transmitted, of which fact I might easily quote many 

 instances. It is important to remember, however, that there is 

 a great difference between the heredity of natural and that 

 of acquired instincts ; for whilst that of the natural instincts 

 admits of no exception, that of the modifications must 

 have become persistent, and assimilated by the organism 

 in a word, automatic, before they are inherited. 



In the light of the evolutional theory " heredity is one of 

 the essential factors of psychological development ; and so 

 mighty and supreme is its influence that it not only preserves 

 instincts, but also creates them." In this light instinct is to 

 be regarded as " an unconscious form of intelligence deter- 



