510 'Journal of Comparative Neurology and Psychology. 



gravity. The conditions were these (fig. 3). 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 con- 

 stant temperature. If Paramoecia show geotropism,^ this irrita- 

 bility 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 Parmaoecia never learned to avoid 

 the vertical leg of the tube. In the end they did not react as vio- 

 lently to the heat and did not, as at first, swim occasionally past 

 the hot metal rod. Also they seem later to develop greater sensi- 

 tivity, reacting to the heat before getting as close to the metal rod. 



If chemicals were not so diffusible and the conditions so hard 

 to govern, an association might be produced between temperature 

 and some chemical stimulus. 



CONCLUSION. 



Paramcecium 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 suit- 

 ability of the movement to accomplish the appropriate result. 



In so far as the tests here apply, there is no evidence of associa- 

 tive memory in Paramoecium. 



The reversing movement above described is in the nature of a 

 positive reaction. 



Hampden-Sidney College, 

 Virginia. 



Moore: Am. Jour. Phys., vol. 9, pp. 238 ff. 



