334 ASA A. SCHAEFFER 



but to establish such an important point the evidence ought 



to be overwhelming. 



SUMMARY 



1 Individuals of three different species of frogs, Rana clamata, 

 R. sylvatica, and R. virescens learned to avoid disagreeable 

 objects, such as hairy caterpillars, in from four to seven trials, 

 or possibly less. Such habits persisted for at least ten days, 

 but this point was not thoroughly tested. 



2 A Rana clamata formed a habit of avoiding earthwomis 

 treated with chemicals in two trials. This habit persisted 

 perfectly for only a short time, covering five trials in about 

 2 2 hours. The habit persisted somewhat imperfectly for five 

 days. After an electric stimulus had been applied, earth-worms 

 were not eaten for seven days although mealworms were eaten. 



3 The avoiding habits were formed in two different ways. 

 In the cases where the hairy caterpillars were avoided, active 

 muscular rejection of the caterpillar accompanied each trial; 

 but in the trials of the chemically treated earthworms, no re- 

 jection, nor any muscular action other than active swallowing 

 of the food object was observed. The latter habit was formed 

 entirely within nervous tissue. 



4 The greater the \'ariety of situations which are success- 

 fully met in an animal's life by a specialized neuro-muscular mech- 

 ism (instinct, chain-reflex, etc.), the more rapid may be the 

 formation of habits involving the mechanism. 



5 Classification of an animal in the scale of intelligence is 

 untrustworthy if based on observations of the behavior involving 

 only one or two neuro-muscular mechanisms. To estimate 

 correctly an animal's intelligence, for present purposes, we 

 must know thoroughly the behavior involving all the import- 

 ant instincts and reflexes ; later, less important behavior must 

 also be taken into consideration. 



6 Inherited instinct will not explain the rapid formation 

 in frogs of habits of avoiding hairy caterpillars and chemically 

 treated earth w^orms. 



7 The rapid formation of habits, and the peculiar process 

 of examination observed while the habits were formed, indicate 

 intelligence of a relatively high order. The probability is that 

 during the examining process the frog was " defining the con- 

 struct "' of hairy caterpillar. 



