26o The Animal Mi1^d 



same reaction, but after this experience had been repeated 

 a certain number of times they ceased to respond to the 

 cotton, although they still took meat eagerly. The point 

 which especially concerns us is this : "I rarely," says Her- 

 rick, "after the first trials, got a prompt gustatory reflex 

 with the cotton." The learning persisted for a day or 

 two. The axolotl learned in a similar way to discriminate 

 between pieces of meat and pieces of wood (276). Hermit 

 crabs, which when young try to take up their abode in all 

 sorts of unsuitable objects, glass balls, for instance, later 

 in Hfe make no such efforts (194). 



Whether or not a movement which brings no favorable 



/results will be dropped off and a state of no movement will 



I take its place depends on how strongly prepotent the move- 



lent is ; upon the strength, that is, of the innate tendency to 



lake it. In the experiments by Professor Bentley and the 



.mter on color discrimination in the creek chub, our first 



I method failed because it required the dropping off, as use- 



hless, of a strongly prepotent reaction, and the substitution 



viof no response at all. Red forceps and green forceps, each 



containing food, were plunged one at a time into the water ; 



the fish was allowed to get the food from the red forceps, 



but the green ones were withdrawn before it had a chance 



to bite. The time which the fish took to rise and snap 



at the forceps was measured by a stop-watch, and in the 



course of 131 experiments the fish had not learned to rise 



to the green any less promptly than to the red. In other 



words, no tendency to drop off the useless movement of 



rising to the green was detected, although later experiments 



,showed that the fish could distinguish between the two 



u forceps. The movement of rising to and biting any small 



I object in the water was so vitally important to the fish 



Uhat it could not be dropped off (757). On the other 



