214 The Animal Mind 



were lost after from six to ten days' interval. Another anem- 

 / one, Tealia, "learned" more quickly than Actinia (127). 



Modification of behavior closely analogous to this was 

 observed in fishes by Herrick. Catfish, when the barbels 

 were touched with a bit of meat, immediately seized it. If 

 a piece of cotton wool were used instead of the meat, they 

 made the 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, showing 

 that neither hunger nor fatigue was involved. Moreover, 

 the "learning" would persist for a day or two. "I rarely," 

 says Herrick, " after the first trials, got a prompt ' gustatory ' 

 reflex with the cotton" (165). In these cases it looks very 

 much as though we had to deal with a real discrimination 

 between stimuli, a type of behavior which will be considered 

 under a later heading. 



83. Varied Negative Reactions to a Repeated Stimulus 



Another way in which reactlfc^ a ^petition of the same 

 stimulus becomes modified is as^^^vs : the animal under a '\ 

 strong stimulus tries , one after c^^^g) different forms of t 

 negative reaction until one of them is successful in getting rid * 

 of the stimulus. Here is a genuine case of trial and error, 

 where, however, different reactions are tried. The Stentor 

 furnishes us with a typical example of this : when attached by 

 its stem and stimulated strongly a number of times in suc- 

 cession, it first tries the ordinary negative reaction, bending 

 over and to one side. Next, it reverses momentarily the 

 direction in which its cilia are whirling. If this, several 

 times repeated, does not succeed in getting rid of the stimulus, 

 the animal contracts strongly upon its stem. This also is 

 continued for some time, but if the stimulus is kept up, too, 

 the Stentor finally breaks away and swims off (203). 



