1898.] on Instinct and Intelligence in Animals. 579 



tion, but having their origin in the germinal substance. But into 

 a consideration of this hypothesis I cannot here enter. Without 

 assuming a dogmatic attitude, I am now disposed to regard the direct 

 transmission of acquired modes of behaviour as not proven. 



Thus we come back to the position assumed at the outset — that 

 heredity plays a double part. It provides, through natural selection 

 or otherwise, an outline sketch of relatively definite behaviour, racial 

 in value ; it provides also that necessarily indefinite plasticity which 

 enables an animal to acquire and to utilise experience, and thus to 

 reach adaptation to the circumstances of its individual life. It 

 becomes therefore a matter of practical inquiry to determine the 

 proportion which the one kind of hereditary legacy bears to the other. 

 Observation seems to show that those organisms in which the en- 

 vironing conditions bear the most uniform relations to a mode of life 

 that is relatively constant, are the ones in which instinct preponder- 

 ates over intelligent accommodation ; while those in which we see 

 the most varied interaction with complex circumstances, show more 

 adaptation of the intelligent type. And the growth of individual 

 plasticity of behaviour in race development would seem to be accom- 

 panied by a disintegration of the definiteness of instinctive response, 

 natural selection favouring rather the plastic animal capable of 

 indefinitely varied accommodation than the more rigid type, whose 

 adaptations are congenitally defined. 



I have dealt, it will be observed, only with the lower phases and 

 earlier manifestations of intelligence. Its higher development, and 

 the points in which it differs from the more complex modes of human 

 procedure, offer a wide and difiScult field for careful observation and 

 cautious interpretation. I have recently attempted further investiga- 

 tions in this field, but tliey concern rather the relation of intelligence 

 to logical thought than that of instinct to intelligence, which forms 

 the subject of this discourse. 



[C. LI. M.] 



