HABIT FORMATION IN FROGS 323 



frog snapped up the worm, made several wild hops, and then 

 dropped it. 



Tenth day. Earthworms, meah\orms, and cockroaches were 

 placed into the cage, but none were eaten or even noticed. 



On the eleventh, twelfth and thirteenth days nothing was 

 eaten. 



Fourteenth day. Three mealworms were eaten but there 

 \\as no reaction to earthworms. 



Fifteenth day. The frog ate two mealworms. Following 



these a normal earthworm was presented, but was unnoticed 



for ten minutes. Two more mealworms were then eaten in 



rapid succession. 



CONCLUSIONS 



The experiments cited illustrate the formation of a habit in 

 at least five different cases as follows : Rana clamata (medium) 

 avoided hairy caterpillars after at most four trials (the first 

 two possible trials on July 26 may have had nothing to do with 

 the formation of the avoiding habit) ; Rana sylvatica formed 

 the habit in seven trials ; Rana virescens formed the same habit 

 in four trials, three on one day and one on the following day; 

 Rana clamata (medium) learned to avoid chemically treated 

 earthworms after two trials (after only one trial if the chemical 

 effect only is considered) ; the large Rana clamata formed the 

 avoiding habit only after a large number of trials, and then 

 possibly only because an electric stimulus was employed ; both 

 the Rana clamata refused all food for three days after a single 

 experience with the electric shock. It may be pointed out 

 that in the case of Rana clamata (medium) the inhibition of 

 the feeding instinct did not affect the habit of leaving alone 

 earthworms and eating mealworms. With regard to the large 

 Rana clamata, we cannot be sure whether the habit of avoiding 

 earthworms and eating meal worms was established wholly by the 

 single application of the electric stimulus, or whether the habit, 

 already partly formed by the effect of the chemically treated 

 worms, was only completed by the electric shock. 



Little attention was paid to the persistence of the habits 

 which the frogs forraed. After the application of the electric 

 shock no earthworms were eaten by Rana clamata (medium) 

 for II days, although mealworms were eaten freely. In the 

 first series of experiments the habit of avoiding hairy cater- 



