HABIT FORMATION IN THE FIDDLER CRAB 



BY BENJAMIN SCHWARTZ AND S. R. SAFIR 



From The Biological Laboratory, Cold Spring Harbor 



Albrecht Bethe (1898) was the first one to investigate asso- 

 ciative memory in Crustacea. After analyzing the normal be- 

 havior of the green crab, Carcinus moenas, on the basis of the 

 structure of the nervous system, Bethe endeavored to discover 

 whether the animal could modify its behavior and thus profit 

 by experience. He liberated a crab in an aquarium containing 

 a cephalopod, Eledone, in the darkest corner. The crab, fol- 

 lowing its instinct to hide, ran to that corner and was imme- 

 diately seized by the squid. At this point the experimenter 

 interfered, and quickly freeing the animal from its captor, 

 placed it again in the lighted portion of the aquarium. The 

 animal ran back to the dark corner and was again seized by 

 the squid. This experiment was repeated five times with one 

 individual and six times with another, without any evidence 

 that the animal learned to avoid the dangerous corner. Bethe 

 then tried another experiment. He baited a crab with a piece 

 of meat and maltreated it every time that it snapped at the 

 bait. This was repeated a number of times, and as in the^pre- 

 vious experiment, he found no modification in the animal's 

 reaction to the stimulus. He, therefore, concluded that the 

 activities of Carcinus are limited to reflexes and instincts, the 

 animal being incapable of exercising any higher mental faculties. 



Yerkes (1902) objects to Bethe's conclusion on two grounds: 

 (1) He maintains that the data is altogether insufficient to 

 warrant any generalization, and (2) that the experiments are 

 of such nature that negative results based on more sufficient 

 data would still be inconclusive proof of the animal's inability 

 to profit by experience. It is evident that Bethe endeavored 

 to suppress two fundamental instincts, namely, fear and hunger. 

 To expect an animal to modify these after five or six experiences 

 is almost preposterous. Yerkes therefore tested the American 



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