AN ANALYSIS OF THE LEARNING PROCESS IN THE SNAIL 31 



TABLE Yl—iContinued) 



Snail Snail Snail Snail 



6 7 8 14 



C. Stimulus Pressure -— — 



Total number of trials 30 20 17 20 



Total number of stimuli followed bv response . . 13 11 3 5 



Per cent of stimuli followed by reaction 43.3% 55% 15.5% 25% 



Total number of reactions 64 67 24 19 



Av. number of reactions per trial 2 . 13 3 . 35 1.41 . 95 



Av. number of reactions in only those trials in 



which response occurred 4.92 6 . 09 8 3.8 



Total time of reactions in minutes 1 . 28 1 . 35 0.5 . 38 



Av. time per reaction in seconds 1.2 1.2 1.25 1.21 



Av. number of reactions per minute 64 . 16 64 . 16 48 49 . 54 



D. Stimulus Food and Pressure 



(Second series) 



Total number of trials 50 50 50 50 



Total number of stimuli followed bv response . . 16 36 44 25 



Per cent of stimuli followed by reaction 32% 72% 88% 50% 



Total number of reactions 123 173 158 120 



Av. number of reactions per trial 2 . 46 3 . 46 3.16 2.4 



Av. number of reactions in only those trials in 



which response occurred 7 . 68 4.8 3 . 59 4.8 



Total time of reactions in minutes 2 . 3l 3 . 78 3 . 28 2 . 53 



Av. time per reaction in seconds 1.21 1.31 1 . 24 1 . 26 



Av. number of reactions per minute 49 . 54 45 . 8 48 . 38 47 . 61 



5. Summary of Observations 



1. All observations and experiments were made on Physa 

 gyrina Say while suspended from the surface film in a dish of 

 filtered tap-water. In this position the lower surfaces of the 

 foot and head are exposed and the movements of the mouth 

 are visible. 



2. When food (lettuce) or an inert substance (glass rod) is 

 quickly applied to such a snail on or near the mouth and im- 

 mediately withdrawn there results a response which consists of 

 one or more opening and closing movements of the mouth. A 

 single opening and closing of the mouth is referred to as a reaction. 

 A response consists of one or many reactions in succession and 

 takes place after the withdrawal of the stimulating substance. 



3. Before the snails were used they were " tamed " b}^ handling 

 until they no longer visibW reacted to the mechanical disturb- 

 ances incidental to the experiments. 



4. All experiments were condticted under approximately uni- 

 form physical conditions, that is in filtered tap water at room 

 temperature and with constant light intensity. 



5. In all tests except those of the preliminary series each 

 snail was used at intervals of fortv-eight hours. It was allowed 



