244 YERKES 



The following are the results of ten trials with two animals. 



Number I . Number 2. 



es. Trial. Time in Minutes 



1 ........ 23 



2 .......... 10 



3 - -41 



4 .......... 3 



5 .......... 2^ 



6 .......... 61 



7 .......... 7 



Crab number I almost invariably moved directly toward the 

 meat and searched for an opening in the screen along the side of 

 the aquarium nearest the meat, thence it would move to the 

 middle of the screen and find the opening. Number 2 just as 

 uniformly followed the edge of the screen, climbing up one side, 

 along the top, down the other side, and across the bottom cease- 

 lessly until it chanced to get near the opening. 



The paths for the first trials were complex and devious, but 

 in the later trials they were almost direct lines to the meat. 



There was little evidence of the use of vision in the finding of 

 the opening in the screen. The animals seemed to be directed 

 chiefly by the stimulus from the food. 



Additional evidence of the ability of Carciints to profit by ex- 

 perience is furnished by the following observation. It was the 

 habit of the experimenter to catch the animals in a hand-net, take 

 them from the water and use them for various experimental pur- 

 poses. At first the crabs did not react otherwise to the approach 

 of the experimenter with the net than to other large objects, 

 but after a few days it became much more difficult to capture 

 them for they had learned to avoid the net. 



