184 PRIMITIVE TYPES OF INTELLIGENCE 



dark hole if there is any within reach, and with its whole 

 energies bent upon getting away from the large creature 

 into whose hands it is taken, what wonder if the devil fish, 

 if it would otherwise be remembered, should be temporarily 

 forgotten. 



The second experiment likewise is one which involves the 

 conquest of a strong instinctive proclivity and it includes 

 also too small a number of trials to be in any way con- 

 vincing. 



The later experiments of Yerkes on Carcinus were more 

 fortunate in yielding positive results. The crabs were placed 

 in a box one end of which led to an aquarium. The end 

 nearest the aquarium was divided so as to afford a right and 

 a wrong path to the water. With successive trials the crab 

 came to learn, although with extreme slowness, to choose 

 the right path. Other simple labyrinths were employed 

 and the crab in each case succeeded, after a sufficient number 

 of trials, in learning the way to the water. The work of 

 Cowles on Ocypoda yielded confirmatory results, although 

 the idiosyncrasies of the animal caused the results to be 

 somewhat less clearly defined. 



Experiments similar to those on Carcinus were performed 

 by Yerkes and Huggins on the crayfish. A simple labyrinth 

 was constructed consisting of a box having a small compart- 

 ment at one end, and an opening at the other leading to an 

 aquarium. From the open end a median partition extended 

 back a short distance, and one of the passages so formed 

 was closed with a glass plate. The crayfish liberated from 

 the small compartment was provided with a choice of two 

 paths only one of which would lead it to the water; and the 

 endeavor was made to ascertain if the crayfish, after a number 

 of trials, would unerringly choose the right path. The 

 crayfish used were put through a number of preliminary ex- 



