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 surroundifigs, 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 
