50 ANIMAL INSTINCT AND INTELLIGENCE 



system through increasingly complex stages has been associated 

 with a corresponding evolution of mind, and there is considerable 

 justification for doubting whether animals devoid of a nervous 

 system, or possessed of a very imperfect one, are endowed with 

 more than a dim consciousness or awareness of existence, or are 

 capable of manifesting either Instinct or Intelligence. 



An animal which inherits the power of performing more or less 

 complex actions helping to adjust it to its ^surroundings, independ- 

 ently of experience or instruction, is said to display Instinct, and 

 such actions may be termed instinctive. They differ from Reflex 

 Actions in being more elaborate, and many of them are partly or 

 entirely spontaneous. But our knowledge is at present too in- 

 complete to enable us to draw the line between actions which are 

 of reflex character and those which are instinctive. It is only 

 when dealing with the higher Invertebrates and the Vertebrates 

 that we can use the latter term with any degree of certainty. The 

 Birch- Weevil (see vol. iii, p. 394), for instance, certainly displays 

 instinct when she constructs an elaborate leaf-funnel for the re- 

 ception of her eggs. This very complicated piece of work is per- 

 formed, so far as we know, with unerring certainty and without 

 previous experience. Nor can the weevil have more than a hazy 

 knowledge of the purpose of her work, which is probably done 

 quite mechanically. 



An animal is said to show Intelligence when it profits by ex- 

 perience, accommodating its actions to the exigencies of changed 

 or changing surrounding. There is an inherited basis to such 

 actions; it is the controlling power which makes them intelligent. 

 The difference between Instinct and Intelligence is explained with 

 admirable lucidity in the following passage from Lloyd Morgan 

 (in Animal Behaviour]'. " Such an animal as a newly-hatched 

 bird or an insect just set free from the chrysalis is a going concern, 

 a living creature. It is the bearer of wonderfully complex auto- 

 matic machinery, capable, under the initiating influence of stimuli, 

 of performing instinctive acts. But if this were all, we should have 

 no more than a cunningly-wrought and self-developing automatic 

 machine. What the creature does instinctively at first it would 

 do always, perhaps a little more smoothly as the organic mechanism 

 settled down to its work just as a steam-engine goes more 

 smoothly when it has been running for a while; but otherwise the 

 action would continue unchanged. Instinctive behaviour would 



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