Smith, Educability of Paramcecium. 505 



must be discovered. With this in view the present study has 

 sought to define the hmits of educabiHty of Paramoecium. 



EXPERIMENTS IN EDUCABILITY." 



The purpose of the following experiments was to determine 

 what kind of modifiabihty is shown by Paramoecium due to recur- 

 ring experiences of the same kind. Less interest attaches to that 

 modification of behavior due to fatigue, which is usually a retarda- 

 tion of movement, than to that modification supposedly due to a 

 rearrangement of structure more suitable to perform the move- 

 ment, which may be called adaptation through practice, and which 

 is usually characterized by more rapid or exact movement. 



Aside from the results bearing on modifiabihty, there are noted 

 below certain movements made by Paramoecium under the condi- 

 tions of the experiments which, to the best of my knowledge, are 

 not spoken of by other observers. 



The experiments fall into three groups: (i) Those in which the 

 animal was stimulated by touch (the meniscus of a capillary tube) 

 the conditions being such that it could react in but two ways in order 

 to escape; and (2) those in which the animal was stimulated by 

 change in temperature; and (3) those in which the animal was fre- 

 quently made to experience two conditions— say A and B which 

 at first occurred simultaneously, and later made to experience con- 

 dition A alone, any difi^erence being noted between the reaction 

 to condition A before it had been combined with condition B and 

 the reaction to it after it had been combined with and again sep- 

 arated from condition B. 



Reactions to touch. The difficulty of observing Paramoecium, 

 or any such free-swimming organism, when it is allowed to swim 

 unrestrained about a slide is known to all who have attempted it. 

 The uncertainty of any results obtained is proportional to this 

 difficulty. It is not important in these experiments to imitate the 

 conditions of real life, so it was decided to make as fixed as pos- 

 sible the conditions of the experiment. 



\ For this purpose a capillary tube was selected of a bore smaller 

 than the length of the Paramoecium and larger than his width. 

 The animal was caught by the upward suction of the tube and the 



* These experiments were carried out mainly in the Laboratory of Psychology of the University of 

 Pennsylvania. 



