AN ANALYSIS OF THE LEARNING PROCESS IN THE 

 SNAIL, PHYSA GYRINA SAY 



INTRODUCTION 



The experiments included in this paper were begun with the 

 purpose of studying the abiUt\^ of snails to discriminate between 

 stimuli. To this end a method was adopted analogous to the 

 salivary reflex method of Pawlow. Its use showed, among other 

 things, a form of modifiability of behavior that could be inter- 

 preted only as learning — the capacity to form associations. 

 The original plan to use this capacity as a basis for studies in 

 discrimination was then changed. The discrimination experi- 

 ments were deferred and the work was continued in order to 

 determine if the snail, which can form associations, can also 

 solve a simple labyrinth. The paper thus falls into two parts. 

 Part one deals with modifiabitity as disclosed by the method 

 of conditioned stimuli — with the power to form simple associa- 

 tions. Part two takes up the further question of the ability 

 of the snail to solve a labyrinth and discusses the relation of this 

 to the formation of simple associations. It is the purpose of 

 the writer to return to the study of discrimination. 



To Professor Jacob Reighard the author is indebted for sug- 

 gesting the problem and for advice during the progress of the 

 work: to Professor John F. Shepard she is indebted for numer- 

 ous criticisms and suggestions. 



I. MODIFIABILITY AS STUDIED BY A METHOD ANALOGOUS 



TO THE PAWLOW SALIVARY REFLEX METHOD 



1. Outline of the Problem 



The snail, Physa gyrina Say, like many other species, has the 

 habit of crawling suspended from the surface film of the water. 

 Its shell is then below and the ventral surfaces of the muscular 

 foot and the head are exposed to view from above. The mouth 

 may then often be seen to open and close many times in suc- 

 cession. Dawson (1911) found that when the region within a 



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