188 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



animal's main food. The cannibalistic tendencies of the slug, together 

 with an unavoidable deterioration due to repeated handling, necessitated 

 a frequent renewal of the animals. 



The methods used in the experiments were simple. The slug was 

 placed on a circular glass plate set horizontally in the bottom of a 

 cuboidal wooden box which was made impervious to light and covered 

 with a thick, black clotli. Precautions were taken to avoid thermal and 

 chemical influences by keeping the box at as equable a temperature as 

 possible and by wiping the plate free from slime before each test. The 

 tests were made only when the animal had definitely oriented itself and 

 was moving ahead in a straight line. Two series were made. In the 

 first series the dorsal tentacle was touched gently with the forefinger. 

 The box was then immediately covered with the black cloth. Observa- 

 tions were made after the lapse of 20 to 30 seconds and the position of 

 the animal noted. The right and left tentacles were touched alternately. 



Results. — The following Table (I.) gives the results of a number of 

 experiments on ten different animals. 



TABLE I. 

 Kesponse to Thigmotactic Stimulation of the Tentacles. 



