72 MIND IN EVOLUTION CHAP. 



It is out of keeping with anything that we know of 

 Thought to suppose that it could reach such a pitch of 

 perfection in relation to a single series of acts, and not 

 show itself in any other way. But it is quite in keeping 

 with the nature of heredity to suppose that in a species to 

 which a certain method of protection has become important, 

 that method should go on under the influence of natural 

 selection, becoming more and more perfect in its mechanical 

 precision. And that instincts no less complex are of this 

 mechanical character is proved by instances which we have 

 already quoted, and to which we might add indefinitely. 

 The truth is, that it is precisely the highly complex 

 development of apparent purpose in certain relations, 

 combined with entire absence of any corresponding mani- 

 festation of intelligence in other respects, that forces us to 

 recognise the purposiveness as only apparent. One has seen 

 incautious writers attributing high unselfishness to an in- 

 sect because it sacrifices itself for young whom it will never 

 see. It is precisely this apparent refinement which removes 

 the action out of the moral category altogether, by making 

 it impossible for the insect to know what it is about. 



3. Instinct and heredity. 



The explanation of instinct by intelligence does not 

 accord with the facts. If the intelligence is regarded as a 

 sort of providential guidance of the animal, the explana- 

 tion founders on the mistakes of instinct and its varia- 

 bility. If it is the animal's own intelligence that is called 

 in, we have seen that it must be an intelligence opposed in 

 the method of its growth and its structure when grown to 

 any sort of intelligence of which we have clear knowledge. 

 These explanations have accordingly given way to the 

 biological theory which explains Instinct by heredity. If 

 a structure can arise through heredity under the influence 

 of natural selection, so also can the function which such a 

 structure performs, and instinct, upon this view, is nothing 

 but the specific function of a definite inherited structure. 

 The evolution of wings is not a separate process from the 

 evolution of flying. The growth of claws and teeth 

 implies the development of a particular habit of fighting 

 and obtaining food. These broad correlations of structure 



