Modification by Experience 303 



is going to do, is obviously the ability to kepp frrnn a.rt.naHy 

 reacting on the instant when the Stimulus acts . To recall 

 a memory idea, to anticipate by slight and invisible move- 

 ments the response one is going to make, implies waiting 

 a brief interval at least before making it in full. Now 

 the development of sense-organs which can receive stimuli 

 conaing from a distance is an absolutely necessary prereq- 

 uisite for the safety of delaying reaction. An important 

 difference exists between the stimuli from objects directly 

 in contact with an organism's body, such as in our own 

 experience give rise to touch, temperature, pain and taste 

 sensations, and those which proceed from objects at a 

 distance, such as light, sound, and odors. This differ- 

 ence consists in the fact that the former have a more direct 

 and instant effect upon the organism's welfare, and in 

 consequence demand more rapid reaction than the latter. 

 A stimulus in immediate contact with an animal's body 

 may have a harmful or beneficial influence at the moment 

 of its impact ; it may be food to be seized or an enemy to 

 be escaped, and the seizing or escaping must be done on 

 the instant ; on the other hand, if an animal possesses the 

 power, belonging in an increasing degree to animals as we 

 go up the scale, of reacting to influences proceeding from 

 objects still at a distance, it may safely delay its reaction 

 when the stimulus is given. The danger is not so imminent, 

 the food is not yet within reach ; the full motor response 

 to stimulation may be suspended for a short interval 

 without imperiling the life interests of the animal. Thus 

 one condition for the development and use of memory 

 ideas is the evolution of sense-organs for the reception of 

 stimuli at a distance. This idea- was first suggested by the 

 writer in 1904 (755) ; a similar conception, developed 

 from the neurological standpoint, appears in Sherrington's 



