Habit in the Earthworm. 



17 



enumerate and evaluate the various external and internal influences 

 on habit-formation ; (d) to ascertain the degree of permanency of 

 the habits and (e) to discover their relations to the anterior ganglia 

 (brain). 



By means of a T-shaped maze constructed from plate glass, 

 specimens of the manure worm, Allolobophora fetida, were tested. 

 The maze was placed with the stem directed toward the light. 

 Across one of the arms a piece of sandpaper was placed and, just 

 beyond it, a pair of electrodes. The other arm was left open so 

 that the worm might escape to an artificial burrow. The worms 

 were driven into the T by light and the chief motive for escape 

 therefrom was the tendency to avoid light. It was the purpose 

 of the test to demonstrate (a) any ability which the manure worm 

 may possess to acquire a direction habit and (b) to associate the 

 tactual experience of contact with sandpaper with the electrical 

 shock which regularly followed the tactual stimulus in case the 

 worm continued to move forward after reaching the sandpaper. 



Trials were made in daily series varying in number from five to 

 twenty. The five-trial series were found, on the whole, most 

 satisfactory. 



Referring now exclusively to the results obtained for a single 

 worm which has been under observation since October, 191 1, the 

 following data may be presented. (1) Allolobophora is capable of 

 acquiring certain definite modes of reaction. (2) Modifications 

 appear as the result of from twenty to one hundred experiences. 

 (3) The behavior is extremely variable because of variations in 

 external conditions and in the condition of the worm itself. (4) 

 There is a tendency to follow the mucous path through the appa- 

 ratus but this is not sufficiently strong or constant to yield perfect 

 results. (5) The following are the chief modifications which have 

 been noted: (a) Increased readiness to enter the apparatus and 

 to desert it for the artificial burrow; (b) apparent "recognition" 

 of the artificial burrow which is used as "exit tube" ; (c) a gradual 

 increase in the number of avoidances of the sandpaper and of 

 contact with the electrodes as a result of the "warning" influence 

 of the sandpaper; (d) the disappearance of the early tendency to re- 

 trace the path through the stem of the T; (e) the similar disap- 

 pearance of the tendency to turn back after progressing well 



