Heredity of Instincts. 3 1 



Instinct may be defined to be 'composite reflex action.' It 

 springs from simple reflex action by successive complications. 

 While in simple reflex action a single impression is followed by a 

 single contraction ; while in the most highly developed forms of 

 reflex action a simple impression is followed by a combination of 

 contractions, in those which we distinguish by the name of in- 

 stinct a combination of impressions is followed by a combination 

 of contractions. This is the case with the fly-catcher, which, 

 immediately after it has left the egg, will seize an insect with its 

 beak. The question of instinct is therefore reduced to this : How 

 can reflex actions, which grow ever more and more complex, spring 

 from simple reflex actions ? 



In order to understand how this transition may be effected by 

 means of an accumulation of experiences, let us, says Mr. Herbert 

 Spencer, take some aquatic animal of a low order, provided with 

 rudimentary eyes. This nascent vision being little more than 

 anticipatory touch, the animal will be able to note the passage of 

 opaque bodies through the water only when they are very near its 

 eyes. Consequently, in most cases these bodies will come in con- 

 tact with its organism, and will so produce a tactile sensation, 

 which will be followed by contractions the necessary effect of a 

 mechanical derangement of the vital force. Hence in this kind 

 of animals there constantly occurs this succession, viz., a visual 

 impression, and a tactile impression, or contraction. 'But if 

 psychical states which follow one another time after time in 

 a certain order, become every time more closely connected in 

 this order, so as eventually to become inseparable, then it must 

 happen that if, in the experience of any species, a visual impres- 

 sion, a tactile impression, and a contraction are continually 

 repeated in this succession, the several nervous states produced 

 will become so consolidated that the first cannot be caused 

 without the others following.' 



If we now assume a more perfect vision in the animal, it will 

 follow that the same bodies will be visible at a greater distance, 

 and that smaller bodies will be visible at a less distance. In such 

 a case, there will be no collision, or it will be slight, and only 

 produced by the small and nearer object. Neither will there be 

 any strong contraction, but a partial tension of the muscles, like 



