Smith, Educability of Paramaecium. 



509 



observations gave nothing but negative results, these results serve 

 to fix the limits of educability in Paramoecium. Although Para- 

 moecium profits by experience, as seen in the above sections, it 

 does not show associative memory such as Loeb v^ould demand 

 as the criterion of consciousness. 



The conditions of the first experiment were these. Paramoecia 

 were placed in a trough having an extremely thin glass bottom and 

 this trough was immersed in a partitioned box containing hot and 

 normally cool water on the two sides, so that the bottom of the 

 trough was kept cool on one half and warm on the other (fig. 4). 

 There was a distinct line, not corresponding exactly to the parti- 

 tion of the under box, at which the Paramcecia approaching from 





Fig. 4. A, alum bath heat screen. B B, light screens. C, cold water supply pipe. H, hot water 

 supply pipe. L, electric light. P, Knife edge partition. R R, overflow return pipes. iS S, supports 

 for trough. T, trough. 



the cool side would turn back. A light was fixed above the trough 

 and a screen interposed so that a shadow fell covering the warm 

 area and a minute part of the cool area beyond the reaction line. 

 The white Paramoecium gives no reaction to light or darkness and 

 it was hoped that by allowing the animals to experience darkness 

 whenever they experienced heat they might, when the heat was 

 removed, react negatively to darkness. This they did not do, 

 however, though one group of Paramoecia were allowed to experi- 

 ence 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 association of heat and 



