action to light or darkness and it was hoped that by allow- 

 ing the animals to experience darkness whenever they ex- 

 perienced heat they might, when the heat was removed, re- 

 act negatively to darkness. This they did not do, however, 

 though one group of Paramoecia were allowed to experience 

 the two conditions together for fifteen hours, one for 

 twenty-four hours, and one for forty hours. 



Another experiment of a somewhat similar kind was 

 performed in which it was tried to bring about the associa- 

 tion of heat and gravity. A small tube was bent into an 

 L shape and, after some Paramoecia had been drawn up into 

 it, was placed so that one leg was horizontal and the other, 

 rising from this, was vertical. At the top of the vertical leg 

 was placed a hot metal rod in contact with the glass and 

 kept at a constant temperature. If Paramoecia show 

 geotropism, (More: Am. Jour. Phys., vol. 9, pp. 238 ff.) 

 this irritability to gravity should be more easily associated 

 with heat than could light, which, although it must make 

 some impression on the organism, does not cause normally 



an avoiding reaction. 



Whenever, the Paramoecia swam up the vertical leg of 

 the tube they received a heat stimulus which caused them 

 at first to jerk backwards and after many random trials to 

 swim downward to the cool water. Although these conditions 

 were kept unchanged for as long as three days the Paramoecia 

 never learned to avoid the vertical leg of the tube. In the 

 end they did not react as violently to the heat and did not, 

 as at first, swim occasionally past the hot metal rod. Also 

 they seemed later to develop greater sensitivity, reacting to 

 the heat before getting as close to the metal rod. 



CONCLUSION 



Paramoecium is educable in that its behavior may be 

 modified to show the results of practice, both in a reduction 

 of the time involved in performing a movement and in the 

 increase in suitability of the movement to accomplish the 

 appropriate result. 



[TWELVE 



