AN ANALYSIS OF THE LEARNING PROCESS IN THE SNAIL 89 



LIST OF ILLUSTRATIONS 



PAGE 



Plate I. Figure 1. — Apparatus used for the simultaneous application to the 

 snail of food and pressure and pressure alone. 



Plate II. Figures 2-7. — Curves showing the distribution of response and re- 

 actions per 10 trials with the food-pressure stimulus. 



Plate III. Figures 8-13. — Curves showing the distribution of responses and 

 reactions per 50 trials with the food-pressure stimulus. 



Plate IV. Figure 14. — U-shaped labyrinth used in the right-left discrimina- 

 tion tests. 



Plate V. Figure 15. — Apparatus used in an attempt to control light condi- 

 tions, the Y-shaped labyrinth, and the reostat used to control 

 the electric current employed in administering the shock. 



Plate VI. Figures 16-18. — Curves showing the distribution of error in the 

 right-left discrimination tests. 



Plate VII. Figures 19-22. — Curves showing the distribution of error in the 

 rough-shock-smooth tests. 



Plate VIII. Figures 23-28. — Curves showing the distribution of error in the 

 tests in which a mechanical stimulus was used in connection 

 with the electric shock. 



