68 DARWINISM AND THE PROBLEMS OF LIFE 



hand touches it. Its flight is purely instinctive ; there 

 cannot be any question of experience, as even the fly 

 that has just issued from the pupa will act in the same 

 way. How has this instinct to fly attained such a 

 perfection? Most certainly by natural selection, since 

 those flies survived longest that had it in the highest 

 degree. Instincts are one of the requisites of an animal's 

 life, and they are therefore subject to natural selection. 



The life of the lower animals is regulated by instincts. 

 How complicated these are will be seen when we come 

 to deal with insects. But, clearly, natural selection 

 must often favour instinctive action in the higher 

 animals as well. When the murderous face of the fox 

 suddenly appears before the resting hare, there is not 

 much time for reflection ; the best thing for the hare to 

 do is to spring aside instinctively and make off. But 

 does the instinct go any farther ? Is the hare's running 

 away also instinctive, and would that be best for the 

 hare? Here we must answer no. In running it is 

 obviously advisable for the animal to reflect. The 

 hare will fly, double, or drop, according to the distance 

 of its pursuer ; and this control of the instinct of flight 

 by the intelligence will certainly be a great advantage 

 to the animal, so that the development of intelligence is 

 favoured by natural selection. 



Intelligence does more than instinct ; it protects the 

 animal even in unforeseen dangers. If you put a 

 mole-cricket on a glass plate its instinct makes it try 

 to bury itself. Intelligence would tell it after a few 

 attempts that it is impossible to scratch up glass, and 

 that flight is the better course in such circumstances. 



