30 ELIZABETH LOCKW'OOD THOMPSON 



TABLE V— {Continued) 

 SXAIL No. 5 — {Continued) 



Average time per reaction in seconds 1 . 54 



Average number of reactions per minute 38 . 96 



Summary Snails 4 and 5: 



Total number of stimuli (trials) 90 



Total number of stimuli followed by response 76 



Per cent of stimuli followed by response 84 . 4% 



Table V shows that movements of the mouth occurred in 76 

 otit of 90 trials, with two individuals, or in 84.4% of the trials. 

 The first series of tests in which the " conditioned " stimulus 

 was used showed reactions occurring in 61 out of 100 trials or 

 61%, when food alone was used as a stimulus (Table II). These 

 differences show the wearing away of the inhibition caused by 

 the secondary stimulus (Table III) and by the experimental 

 manipttlation. The mean number of reactions per response 

 for snails 4 and 5 was 4.84, 0.91 less than for the normal food 

 response and 1.01 more thati in the food-pressure series with 

 trained snails. The inhibition of the response to food by the 

 pressure stimultis has nearly disappeared (^adaptation). 



TABLE VI 



Showing a summary of the reactions of the mouths of four individuals of Pliysa 

 gyrina Say, resulting from (A) food stimulus alone, cf. Table II; (B) food and 

 pressure used simultaneously, cf. Table III; (C) pressure alone, cf. Table IV; (D) 

 food and pressure used simultaneously, 2d series, cf. Table V. The tests were 

 made in filtered tap water on alternating days. The snails had been starved for 

 24 hours preceding the tests. g^^g-j gnail Snail Snail 



6 7 8 14 



A. Stimulus Food — • 



Total number of trials 42 50 60 60 



Total number of stimuli followed by response . . 8 38 47 32 



Per cent of stimuli followed by reaction 19% 76% 78.3% 53.3% 



Total number of reactions 52 247 143 350 



Av. number of reactions per trial 1 . 23 5.14 2 . 38 5 . 83 



Av. number of reactions in only those trials in 



which response occurred 6.5 6.5 3.4 10 . 93 



Total time of reactions in minutes 1.13 5.33 3.23 7.35 



Av. time per reaction in seconds 1.3 1 . 29 1 . 39 1 . 25 



Av. number of reactions per minute 46 . 15 46 . 51 44 . 44 48 



B. Stimulus Food and Pressure 



Total number of trials 250 250 253 250 



Total number of stimuli followed bv response .33 82 53 47 



Per cent of stimuli followed by reaction 13 . 2%, 32 . 8%: 20 .9% 18 .8% 



Total number of reactions 65 337 84 182 



A V. number of reactions per trial . 26 1 . 34 . 03 . 72 



Av. number of reactions in only those trials in 



which response occurred 1 . 96 4.1 1 . 58 3 . 87 



Total time of reactions in minutes 1.2 6. 56 1.5 3.6 



Av. time per reaction in seconds 1.1 1.16 1 . 07 1.18 



Av. number of reactions per minute 65.45 51.72 56.7 50.84 



