330 ASA A. SCHAEFFER 



gree but in kind. While I admit that it is quite possible that 

 it may some time be found to be easier for an animal to inhibit 

 an action than to learn a new one of a similar sort, we have at 

 present no experimental evidence to my knowledge that this 

 is so. Further, our experiments with frogs may be discussed 

 from the viewpoint of discriminative capacities. On this basis 

 the frogs of Yerkes' experiments seem to have discriminated 

 between degrees of light and dark in the first part of the laby- 

 rinth, while in the last part of the labyrinth they clearly formed 

 the habit to perform Certain movements (to get out of the laby- 

 rinth) and to avoid others which they instinctively might not 

 avoid — the glass plate in the visually determined shortest path 

 to the tank — that is, they discriminated between going straight 

 forward and turning to the right or left as the case may have 

 been. These habits were formed by dropping certain instinc- 

 tive movements, just as the frogs in the feeding experiments 

 learned to drop certain instinctive movements. The objection 

 spoken of in the beginning of this paragraph therefore does 

 not seem to deserve consideration until we have further data 

 on this point. 



It is hardly necessary, perhaps, to speak of instinctive avoid- 

 ance of hairy caterpillars. C. L. Morgan seems to think that 

 birds and lizards inherit, somewhat incompletely, the habit of 

 avoiding warningly colored " caterpillars or insects." The in- 

 heritance is incomplete because sometimes the insects are eaten. 

 " But a very small basis of experience, often a single case, is 

 sufficient to establish the association" (7, p. 445). Whatever 

 may be the explanation for the facts cited by Morgan, instinc- 

 tive avoidance of hairy caterpillars by frogs probably does not 

 explain the rapid formation of the avoiding habit, because it 

 clearly cannot explain the more rapidly formed habit of avoid- 

 ing chemically treated earthworms. 



PSYCHIC PROCESSES 



Can the experimental results described in this paper be satis- 

 factorily explained upon purely physiologic grounds, or is it 

 necessary to call in psychic processes to make the explanation 

 adequate ? 



Let us take first the case of Rana clmnata (medium) which 

 formed the habit of avoiding hairy caterpillars by testing with 



