232 BENJAMIN SCHWARTZ AND S. R. SAFIR 



where the animal pauses for about five seconds before going to 

 either corner. 



With these facts before us, we subjected ten animals, seven 

 males and three females, picked up at random, to a simple 

 labyrinth test. Our labyrinth was modelled after the one de- 

 scribed by Yerkes and Huggins, with modifications adapted to 

 the needs of the fiddler crabs. We selected a box 50 cm. long, 

 30 cm. wide, and 30 cm. deep. It was filled to a depth of 12 

 cm. with moist sand, in order to give the animals a natural 

 substratum. By means of glass plates, 12 cm. square, we made 

 a triangular space at the center of one of the narrower ends, 

 with an opening sufficiently large to enable the crabs to pass 

 through. At the corners of the opposite end we cut out open- 

 ings, 8 cm. wide and 5 cm. high, which could be closed by means 

 of glass plates. To prevent the animals from going to the cor- 

 ners of that end of the box which contained the triangular 

 chamber, we placed glass plates extending at right angles from 

 each side of the opening of the chamber to the long side of the 

 box. Adjoining the labyrinth there was another box, 60 cm. 

 long, 25 cm. wide and 25 cm. deep. It was filled with moist 

 sand to a depth of 12 cm, several artificial burrows being made 

 in the sand. By means of an opening at each end of the longer 

 side, the box could be made to commuuicate with the labyrinth 

 on either side. 



At first both corners of the labyrinth were closed by means 

 of glass plates and each of the animals to be tested was given 

 a series of preliminary trials to determine to which side of the 

 box it was inclined to go. As soon as this was determined, the 

 favorite corner was left closed, while the one opposite was 

 opened. The crab was then placed in the chamber by the 

 experimenter, who took up his position three feet behind the 

 box, remaining perfectly quiet. His position afforded him a 

 good view of the animal's movements, which were carefully 

 noted. As soon as the crab was liberated it made a number 

 of efforts to climb up the sides of the glass chamber. In doing 

 this it fell after each attempt, the shock evidently frightening 

 it. It then abandoned climbing, and either ran out of the en- 

 closure very rapidly, or moved out rather cautiously, going 

 to its favorite corner. Here, too, it made attempts to climb, 

 but making no headway against the smooth surface of the 



