1898.] Instinct and Intelligence in Animals. 567 



WEEKLY EVENING MEETING, 



Friday, January 28, 1898. 



Sir James Crichton-Browne, M.D. LL.D. F.R.S. Treasurer 

 and Vice-President, in the Chair. 



Professor C. Lloyd Morgan, F.G.S. Principal of 

 University College, Bristol, 



Instinct and Intelligence in Animals. 



Biology is a science, not only of the dead, but of the living. The 

 behaviour of animals, not less than their form and structure, demands 

 our careful study. Both structure and behaviour are, however, de- 

 pendent on that heredity which is a distinguishing characteristic of 

 the organic world, and in each case heredity has a double part to 

 play. It provides much that is relatively fixed and stereotyped, but 

 it provides also a certain amount of plasticity, or ability to conform to 

 the modifying conditions of the environment. Instinctive behaviour 

 belongs to the former category ; intelligent behaviour to the latter,. 

 When a caterpillar spins its silken cocoon, unaided, untaught and 

 without the guidance of previous experience ; or when a newly-mated 

 bird builds her nest and undertakes the patient labours of incuba- 

 tion, before experience can have begotten anticipations of the coming 

 brood, we say that the behaviour is instinctive. But when an animal 

 learns the lessons of life and modifies its procedure in accordance 

 with the results of its individual experience, we no longer use the 

 term instinctive, but intelligent. Instinct, therefore, comprises those 

 phases of active life which exhibit such hereditary definiteness as fits 

 the several members of a species to meet certain oft-recurring or 

 vitally important needs. To intelligence belong those more varied 

 modes of procedure which an animal adopts in adaptation to the 

 peculiar circumstances of its individual existence. Instinctive acts 

 take their place in the class of what are now generally known as 

 congenital characters; intelligent acts in the class of acquired 

 characters. 



But the study of instinct and intelligence in animals opens up 

 problems in a different field of scientific investigation. They fall 

 within the sphere not only of biological, but also of psychological 

 inquiry. And in any adequate treatment of their nature and origin, 

 we must endeavour to combine the results reached by different methods 

 of research in one harmonious doctrine. This involves difiiculties 

 both practical and theoretical. For those invertebrates, such as the 

 insects, which to the naturalist present such admirable examples of 



2 p 2 



