224 INSTINCT : 



visceral needs are performed amidst practically uniform 

 conditions, that these acts would also tend to exhibit some 

 degree of the same uniformity — whether they are connected 

 with search after or storing of food, with capture of prey, 

 with sexual dalliance, or with the deposition or care of 

 eggs or young. The nerve tissues having to do with 

 any mixed series of habitually recurring impressions and 

 actions, would, in the course of ages, come to be so organi- 

 cally knit together as to permit of the manifestation of 

 a machine-like regularity of habit, approximating to that 

 which is observed in the performance of the simpler acts 

 more immediately dependent upon visceral stimuli. 



The possibility of executing any simple Instinctive Acts, 

 and still more those which constitute a complex series, can 

 only have been built up and definitely organized after suc- 

 cessive generations of animals have been habitually sub- 

 jected to the impressions to which the acts are related, and 

 after such impressions have, at last, invariably led to the 

 particular motor results in question. We owe the first 

 distinct enunciation of this light-giving notion to Herbert 

 Spencer. He says :* — " Let it be granted that the more 

 frequently psychical states occur in a certain order, the 

 stronger becomes their tendency to cohere in that order, 

 until they at last become inseparable; let it be granted that 

 this tendency is, in however slight a degree, inherited, so 

 that if the experiences remain the same, each successive 

 generation bequeaths a somewhat increased tendency ; and 

 it follows that, in cases like the one described, there must 

 eventually result an automatic connection of nervous 

 actions, corresponding to the external relations perpetually 

 experienced. Similarly, if from some change in the 

 environment of any species, its members are frequently 

 brought in contact with a relation having terms a little 

 ♦ "Principles of Psychology," vol. i. p. 439. 



