LEARNING IN PARAMECIUM 73 



A word should be added on the negative cases. We have 

 examined many individuals not reported in the text. Not 

 infrequently the work of whole days came to no issue. But 

 failure was due either to poor cultures, to the technical diffi- 

 culties of the experiment, or to the sluggish inactivity of the 

 subject. A normal Paramecium once brought without injury 

 into a pool of convenient size never failed — provided it remained 

 active after the first few reversals — to show a modification 

 of the type exemplified in the results. 



It appears from the experiments (i) that Paramecium is capable 

 of modifying within a few minutes its usual avoiding reaction; 

 the lateral turn is so increased and prolonged as to permit the 

 animal to reverse its long axis in a narrow circular tube; (2) 

 that the effect of this modification remains for some time 

 independently of external changes induced. Observations of 

 this nature are taken as evidence of learning. The evidence 

 in this case is supported by the fact that during the process of 

 turning, the animal had the appearance of doing a definite 

 thing. Nevertheless, it is questionable whether this kind of 

 "learning" involves consciousness; whether it is not as well 

 interpreted as the result of purely organic processes. 



Further experiments designed to control more closely the con- 

 ditions of the performance, and especially to ascertain the term 

 of the modification induced, are in progress. 



