228 BENJAMIN SCHWARTZ AND S. R. SAFIR 



to light at night. Taking advantage of this tropism, she suc- 

 ceeded in making the crabs come from the shaded side of the 

 box to the side which was artificially illuminated, although in 

 doing this, the animals had to find an opening in the partition 

 which divided the box. The rapidity with which the opening 

 was found increased with successive trials. The same writer* 

 (1910) studied habit formation in the hermit crab, Clibanarius 

 misanthropus. She placed tightly corked gastropod shells near 

 naked crabs. The latter immediately fastened themselves upon 

 the shells, trying to pull out the corks. Since all their efforts 

 to enter the shells were in vain, the animals were observed to 

 relax, and at the end of from six to eight days, they became 

 entirely indifferent to their presence. If at this point of the 

 experiment, shells, similarly sealed but of different shape, were 

 introduced, the crabs began to attack them immediately. These 

 results indicate that Clibanarius not only possesses associative 

 memory but that it is also able to discriminate form. Cowles 

 (1908) found that Ocypoda arenaria could learn to escape from a 

 labyrinth, although it did not learn the position of the exit very 

 accurately. He also found that if he buried a dish of salt water 

 in the sand of their trap, so that the rim of the dish was on a 

 level with the surface of the sand, the crabs learned to climb 

 into the vessel to moisten their gills. 



The experiments described hereafter were performed with the 

 fiddler crabs which inhabit the sand spit at Cold Spring Harbor, 

 Long Island. They live on sandy beaches as well as on mud 

 flats, where they construct burrows about one foot in depth. 

 They are diurnal in their habits, and on bright, sunny days 

 they may be seen in large numbers, running hither and thither, 

 feeding and burrowing. The males are particularly striking 

 because of the large cheliped with which they perform curious 

 antics, and which they use as a weapon for combat. When 

 the tide comes in the crabs retreat to their burrows, where they 

 remain until the area above them is again exposed by the reced- 

 ing waters. Their general activities are therefore interrupted 

 at regular intervals, during which they remain perfectly quiet. 

 Their behavior appears to be regular and unchanging, almost 

 stereotyped. 



There are two species of fiddler crabs on the sand spit, Uca 



*This paper was not available to us. We read an abstract of it in The Jour, of 

 An. Beh., Vol- I, No. 6, pp 450-451, 1911. 



