HABIT FORMATION IN THE FIDDLER CRAB 229 



pugnax and Uca pugilator, the most distinguishing characteristic 

 of the latter being a ridge across the palm of the large cheliped. 

 In the experiments the pugilators were utilized almost exclu- 

 sively, because of their greater vigor and resistance. The pugnax 

 forms did not thrive in captivity, and became very sluggish. 

 The work with them could not progress very rapidly. 



The aim of the experiments was to determine (1) whether 

 the fiddler crabs can form a simple labyrinth habit, (2) whether 

 the habit is retained for a few days, and (3) whether the habit 

 can be broken up. 



When the crabs are placed in a wooden box which is about 

 one-half full of moist sand or mud, they immediately begin to 

 seek a means of escape. They usually run to the side opposite 

 which the experimenter is standing, and climb up the sides, 

 near the corners, by inserting the sharply pointed ends of their 

 ambulatory feet into the rough surfaces of the wood. They 

 climb gradually and do not seem to become discouraged by 

 failures. As soon as they reach the top of the box, they escape. 

 It was observed that the animals showed a decided tendency 

 to go to a particular corner, even though escape was rendered 

 impossible by inserting glass plates against the sides. Table 1 

 gives the records of twelve individuals, showing the corner to 

 which they went, as well as the average interval between two 

 successive trials. 



12 35 45 " 1 " 17 " 30 10 3 2 



An examination of the above table shows (1) that the interval 

 between two successive trials varies from about one and a half 

 to two minutes, (2) that the animal's desire to liberate itself 

 from the trap persists even when thirty-five trials are given, 



