THE LEVELS OF BEHAVIOUR 151 



animal, as pure memory, as motor habit, as individual acquire- 

 ment, as instinct and perhaps as heredity. 



Pure memory is the retention in present consciousness of past 

 states of consciousness. '' Past " means here the immediate 

 intuition of duration and is not " the physical past." (In the 

 passage of nature entropy increases, so that of two events that 

 one which displayed the lesser entropy was the " physically " 

 past one.) The retention of past states of consciousness is 

 incomplete and ultimately fails as the animal becomes senile. 

 We call it memory, the imagination of past things, visualiza- 

 tion of past things and so on. It is elementary and in- 

 definable. 



Motor-habit means that behaviouristic activities acquired with 

 difficulty become facile, or habitual, are performed automatically 

 and may become instinctive in the off"spring of the animal in which 

 they were acquired. These matters we shall examine more 

 closely in the further sections. 



546. Trial, Error and Experience. Behaviour that merely 

 involves random acts that are tried again and again until one is 

 successful is probably exceptional among animals. It may be 

 realized in the avoiding-reaction of Paramcecium (Section 52^) 

 or by such behaviour as that of a Vorticella upon which a stream 

 of particles is allowed to fall. The animal may respond, first 

 by a reversal of its ciliary motion, then by bending to one side 

 or the other and finally, should the previous trials fail to avoid 

 the irritant, by breaking its stem and swimming away. If such 

 experiments are repeated many times on the same individuals, 

 and if there is always the same sequence of trials, there is no 

 action, in our sense of the term. 



The labyrinth experiments are typical of a large class that 

 demonstrate experience. The animal is placed near food which 

 it can smell but which it can apparently approach by several 

 alternative paths, only one of which, however, enables it to 

 obtain the food. It will try the various paths at random, finally 

 traversing that one which is successful. If now the same experi- 

 ment is repeated many times with the same animal and if the 

 latter finally chooses the right path at once, there is true action. 

 Many variants of such an experiment have been made with much 

 the same results and apart from academic evidence ordinary 

 observation leads to the same conclusions : thus a man in a 



