A NOTE ON LEARNING IN PARAMECIUM 



By LUCY M. DAY AND MADISON BENTLEY 



From the Cornell Lahorutory for Comparative Psychology 



ONE FIGURE 



If Paramecium learns we may expect to find its learning 

 based upon some slight modification of that " action system " 

 which is brought into function by the common activities of the 

 organism. Modification, however, is not in itself the equivalent 

 of learning. It suggests learning only when it is preserved by 

 the animal and used as an " acquirement " upon a later occasion. 



The experiments which follow sought to induce such a modifi- 

 cation and to record — should the change persist — its subsequent 

 effects. The protozoa were isolated and studied individually; 

 for it seemed important to duplicate, so far as was possible, the 

 experimental control exercised in the study of the higher forms 

 of life. 



With this end in view, the writers made use of the capillary- 

 pool, drawing a single Paramecium into a glass tube the diameter 

 of whose lumen was a little less than the animal's length. Then 

 by applying the lips to the larger end of the tube, the pool of 

 culture-water containing the subject was drawn up and away 

 from the tip of the tube and reduced to .5-2.0 cm. in length. 

 The tube was then stuck with bits of wax to a long strip of glass 

 for support and placed at once under the microscope at low 

 power. The observer watched the pool continuously, recording 

 with a key and kymograph backward and forward movements, 

 wheeling movements at the meniscus, partial turns across the 

 tube, and complete changes of direction (reversal). Paramecium 

 succeeded in changing direction by bending its anterior end at 

 the oral groove until the backward beat of the cilia carried it 

 along the wall of the tube and to the rear.^ 



1 Mter the method had been developed, an article on The Limits of Educa- 

 bility in Paramecium, by Stevenson Smith, appeared in the Journal of Comp. Neur. 

 and Psychol., vol. 18, p. 499, 1908. Smith observed reversal in the capillaiy-tube 

 and remarked that the time was in some cases reduced in the course of 12 hours 

 or more "from 4 or 5 minutes to a second or two" (p. 507). He seems not to have 

 observed the process of reduction or to have controlled chemical changes in the 

 tube. It is worthy of remark that the present writers detected an occasional 

 turn towards the oral side. This unusual performance may have been due to con- 

 tact with the tube; they are at present unable to say, 



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