MIND IN EVOLUTION 513 



whole organism, or of a large part of it, which automatically 

 make towards securing physiological equilibrium in refer- 

 ence to particular stimuli. Thus an organism moves towards 

 or away from light and heat, electric currents and diffusing 

 chemical reagents, water currents, and the earth and so on. 

 It must not be said that heliotropic animals desire the light 

 or dislike the darkness ; the tropisms are more or less forced 

 movements which work automatically like a gyroscope. 



Our evolutionary theory is that reflexes and tropisms are 

 economical automatisations, enregistrations, or organisations 

 of capacities which are continually being called into action 

 in the ordinary life of the creature. They require neither 

 thought nor endeavour; they are ingrained and almost as 

 much part of the constitution as, say, breathing movements. 

 Their survival value is (1) that they admit of the rapid 

 automatic execution of life-preservative or species-preserva- 

 tive movements (an automatism for which in unusual con- 

 ditions there may be a heavy tax to pay) ; and (2) that they 

 leave the organism more free to use, if it can, the second 

 string of purposive endeavour. 



(/) The main line continues in a kind of behaviour which 

 shows evidence of ' learning ', of utilising previous experi- 

 ence to compass an end which is not necessarily immediate. 

 The note of inference is beginning to be sounded. There 

 is experimentation and correlation at a higher level than that 

 of the starfish. It is the dawn of intelligence, and may be 

 illustrated by cases like the following. A young octopus 

 trying to capture a hermit-crab is stung by the sea-anemone 

 which is the crustacean's partner. It avoids further en- 

 counters. Old octopuses, however, learn to extract the her- 

 mit-crab without touching the sea-anemone. Prof. Lloyd 

 Morgan calls this profiting by experience through the exer- 



