Modification by Experience 



221 



completely baffled for a time, but succeeded in learning the 

 new habit (47 1 ). Ants of the species Stenammafulvum piceum 

 have been tested in a labyrinth by Fielde. The observations 

 indicated that this ant's tendency to be guided by the chemical 

 traces of its own footsteps militated to a certain extent against 

 shortening the path by dropping off useless turnings. Each 

 ant followed her own previous trail through the labyrinth to 

 the nest. Yet some tendency for the movements to become 



FIG. 14. Labyrinth used by Yerkes in experiments on the frog. A, box open- 

 ing into maze ; E, entrance ; T, tank ; G, glass plate ; P, partition ; 7C, 

 electric circuit whereby animal could be given shock on entering wrong 

 passage; C, K, cells and key; R, R, red cardboard; W, W, white card- 

 board. 



automatic and independent of the smell clew was shown by 

 the fact that when an ant had gone over the path many times, 

 a portion of the track might be obliterated without inter- 

 rupting her course 1 (118). 



A simple form of the labyrinth method has been used on 

 fish (Fundulus), which were kept by a screen in the sunny end 

 of an aquarium, the darkened end being also the place where 

 they were fed. One upper corner of the screen was cut out. 

 In a couple of days, allowing six or eight trials a day, the fish 

 learned to swim straight up to this corner (394). A more 

 complicated labyrinth was also used, but the time required 



1 Cf. the observations of Pieron referred to on p. 94. 



