34 ELIZABETH LOCKWOOD THOMPSON 



hours. Similar results were obtained from vSnails 5, 6, 7, 8 and 

 14 (Tables IV and VI-C, pp. 25 and 31). 



17. Cessation of pressure response in trained snails. — Imme- 

 diately following the ninth response to pressure of trained Snail 

 No. 4 (paragraph 16) seven successive applications of pressure 

 gave no response ; 48 hours later ten applications gave no response ; 

 96 hours after the last response ten applications failed to give 

 any response. Similar results were obtained with the other 

 five snails. Cessation of respotise to pressure after training is 

 sudden and final (Tables IV and VI-C, pp. 25 and 31. 



18. One hundred and twenty hours after the last response to 

 pressure of Snail No. 4 (paragraph 16) a scries of 50 trials was 

 run on this snail by the simultaneous application of food and 

 pressure. Response followed the first three trials and occurred 

 in 86% of the subsequent trials (cf. paragraph 15), with an 

 average of 4.9 reactions. Similar results were obtained w^ith 

 Snail No. 5. The average number of reactions per response was 

 4.84 for the two snails, 0.91 less than for the normal food re- 

 sponse (paragraph 10) and 1.01 more than in the first food- 

 pressure series (paragraph 15). The interference of the pres- 

 sure stimulus with the response to food has nearly disappeared 

 (Tables IV and VI-B, pp. 25 and 30). 



19. The average number of reactions in the food-pressure 

 response is less than the number in the normal food response. 

 The numbers for the six snails in their numerical order is 3.96, 

 3.62, 1.96 (Table III, p. 13), 4.1, 1.58 and 3.87 (Table VI-B, 

 p. 30). The average for the six snails is 3.18. Application of 

 pressure to the foot at the same time with food to the mouth 

 shortens the response. 



20. The average duration of the reaction is less in the food- 

 pressure responses than in the normal food response. The num- 

 ber per minute for the six snails in numerical order is 51.84, 

 51.92, 65.45, 51.72, 56.7, 50.84 (Tables III and VI-B, pp. 13 and 

 30). This is a mean distribution of 54.74, or 8.49 reactions per 

 minute in excess of the normal food response (paragraph 12). 



21. In the food-pressure series, the average number of reactions 

 per ten trials increases irregularly toward the end of the series, 

 except in the case of Snail No. 4. The average number of 

 responses per ten trials shows a more uniform rise (Table III-A, 

 p. 19, figs. 2-7, Plate II). 



