512 THE EVOLUTION OF MIND 



but the purposiveness has not reached a perceptual level. 

 Consciousness is at work, and its " precise function in sen- 

 sori-motor action is to grasp the unique combination of stim- 

 uli, each of which having its special reaction modified by 

 the concomitant reactions, there follows a response appro- 

 priate to the unique situation as a whole ' (Hobhouse, Mind 

 in Evolution, 1915, p. 62). 



(e) With the establishment of a nervous system there was 

 opened up the possibility of a new kind of hereditary autom- 

 atisation or organisation, that of reflex actions and tro- 

 pisms. The former are usually movements of parts of the 

 animal, the latter movements of the whole creature. A re- 

 flex action is the predetermined result of the activation of 

 an inborn structural arrangement of receptor, conductor, and 

 effector, which gives a uniform response to a given stimulus. 

 It may be very perfect from the first, or it may improve 

 by practice, or it may result from individual habituation: 

 but typically it is an outcome of pre-established hereditary 

 organisation, definite linkages of sensory neurons, associa- 

 tive neurons, motor neurons, and muscular elements. In 

 effect reflex actions seem purposive, but in process they are 

 organisational. If there was originally an operative pur- 

 posiveness, it has receded into pre-formed structure. 



Our pictures are of the sea-anemone closing its tentacles 

 on a victim, of the nestling opening its mouth at the touch 

 of food in its mother's beak, of the starfish surrendering an 

 arm in the spasms of capture, of the young mammal sucking 

 whatever is put into its mouth. Antecedent to reflexes there 

 is more or less random flow of activity which is now and 

 then definitised in experiment and endeavour. Reflexes im- 

 ply the establishment of definite channels for the flow. 



Tropisms are more or less obligatory movements of the 



