68 Bulletin of Laboratories of Denison University. [Voi. xii 



make the simple reflex of seizing the food under the stimulus 

 applied to any part of the barblets or skin, and doubtless utiliz- 

 ing both gustatory and tactile sensations, the gustatory 

 factor is eliminated by the substitution of cotton wool 

 for the meat. The tactile sensation alone proves to be 

 sufficient to set off the reflex after the train- 

 ing previously given. I'he stimulus is, however, never 

 followed by satisfaction and is soon given up, the fishes after 

 further practice not reacting to the tactile stimulus alone. If, 

 however, the gustatory sensation is added, by the substitution 

 of meat for the cotton, the original reflex is given as promptly 

 as before. This would seem to indicate that, while the tactile 

 sensation alone is not sufficient to maintain the reflex, the addi- 

 tion of the gustatory element is sufficient, and therefore that 

 the gustatory element is the essential element in setting off the 

 reflex. This h)'pothesis was tested by an extensive series of 

 experiments similar in plan to those last described. 



In general there was no noticeable difference between the 

 reaction to the white cotton and that to the red, though in 

 some cases, especially toward the end of the series of experi- 

 ments, after the fishes had learned to pay no attention to white 

 cotton when touched at any point by it, they would sometimes 

 turn and touch the red cotton with the lips or a barblet, imme- 

 diately to turn away again without biting the cotton as they did 

 at first. The reaction is not the quick turn and instant seizing 

 of the bait which I have termed the "gustatory reaction," but 

 a more deliberate movement similar to what I termed above 

 the "tactile reaction." This occurred only when the cotton 

 was in plain view at the time of the contact and is probably in 

 this case partly a visual response called forth by the similar ap- 

 pearance of the red cotton and bits of beefsteak on which they 

 were habitually fed. It was not by any means constant, for, in 

 general, after the first few days contact with neither color of 

 cotton called forth any response whatever. 



Alter this result was reached, I dipped the pledgets of 

 white cotton in the filtered juice of fresh beef and touched the 

 body surfaces and barblets with them in the same way as be- 



