THE EDUCABILITY OF A SNAIL 57 



snail's mouth was touched with a little piece of 

 food, such as lettuce, there followed a number 

 about four was common of rapid mouth-move- 

 ments, opening and closing, in fact. These obviously 

 correspond, in the logic of the experiment, to the 

 mouth-watering of Pavlov's dog. 



The next step was to find a practicable secondary 

 stimulus, and that used was pressure on the snail's 

 foot or creeping sole with a clean glass rod. This 

 does not normally evoke any mouth-movement, 

 except in rare cases, which are readily explained. 

 The next step was to apply simultaneously the two 

 stimulations, the touch of food near the mouth 

 and the pressure of the glass rod on the foot. To 

 this for a time no answer at all was given. It was 

 not till the snails had been tried sixty to one hundred 

 and ten times that they began to answer, but after 

 the Rubicon was crossed they answered back all 

 the rest of the total of two hundred and fifty trials. 

 It was noteworthy, however, that the number of 

 mouth-movements in a single response did not 

 reach so high an average as was exhibited when the 

 food stimulus was used by itself. The snails that 

 gave the normal answer-back to the two stimuli 

 applied simultaneously were regarded as " trained," 

 and were ready for the next and crucial step in the 

 experiment. Forty-eight hours after the comple- 

 tion of their training the snails were tried with the 

 foot-pressure stimulus by itself. The dux of the 

 class gave the proper mouth-moving answer the 

 first seven trials right away; two other answers 



