HABIT FORMATION IN THE FIDDLER CRAB 



231 



light, but it was found that when the latter was eliminated, the 

 preference was not changed. Hence some other explanation had 

 to be sought. An examination of the male crab shows it to be 

 unsymmetrical, owing to the possession of the large cheliped, 

 which may be either on the right or the left side of the body. 

 This suggested the hypothesis that the right handed males are 

 inclined to go to the right side, and the left handed males to 

 the left side. Since the females possess no large cheliped, they 

 were expected to be neutral in this respect. That these expec- 

 tations were fairly borne out maybe seen in table 2. 



Fig. 1. Showing labyrinth and adjoining box. Dotted lines represent glass 

 plates, and circles represent burrows. 



An examination of the data presented above shows that 70% 

 of the males made a majority of their movements to the corner 

 corresponding to the position of their cheliped. About 10% 

 showed no preference for either side, while the remainder, about 

 20%, went to the side directly opposite to the expectation. But 

 the fact remains that about 90% are inclined to go to a par- 

 ticular side. The number of trials for the right handed males 

 is 226 to the right and 124 to the left, giving a ratio of about 

 2:1, that of the left handed males is 228 to the left and 122 to 

 the right, giving a similar ratio. The females made 114 attempts 

 to the right, 113 to the left, and 123 to the center, "giving a ratio 

 of 1:1:1. By an attempt to the center is meant a direct move- 

 ment from one end of the box to the center of the opposite end, 



