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



part, or the side of the body or the free pelvic fin. The reflex 

 is immediate and unmistakable, more sharply defined than I 

 usually get by contact with the meat of the same mussel. The 

 experiment was many times repeated, always with the result 

 that the jet of water was ignored or avoided, while the jet of 

 mussel or clam or crab juice was eagerly sought, the fish usually 

 snapping at the end of the pipette. 



I have carried out no systematic chemical experiments to 

 determine the gustatory preferences of the fishes, having shaped 

 my experiments so far as possible along the lines of the normal 

 feeding habits of the species studied. Nagel and some other 

 previous students of these problems have relied chiefly on re- 

 actions to unpleasant stimuli and the reader is referred to their 

 works, though I consider this a less satisfactory line of inquiry 

 than the study of normal reactions to food substances. The 

 few fragmentary observations which I have made with chemical 

 stimulants I shall, however, record in their appropriate places. 



Specimens of hake were tested with a 0.2^ solution of 

 hydrochloric acid made up in distilled water, the acid being 

 directed against the body by means of a fine pipette. The 

 dorsal and ventral fins, the sides of the body and the lips were 

 tested. When first tested on the fins one hake turned and tried 

 to take the pipette, much as he did with the clam juice. After- 

 wards this fish, as well as all the others from the first, seemed 

 rather to dislike the acid and would swim slowly away. There 

 is no constant reaction, however, and in fact the fishes act very 

 much as they do when a jet of simple sea water is directed 

 against them. They do not appear to dislike the acid intensely. 

 Later I tested these fishes with a i ^ solution of hydrochloric 

 acid in sea water. This is decidedly unpleasant and is uni- 

 formly avoided. 



The experiments recorded seem to show clearly that the 

 hake receives both tactile and gustatory stimuli by means of 

 the free fin rays and to some extent doubtless by other parts of 

 the outer body surface. What role may be played by the 

 sense of smell remains obscure. To test the powers of locating 

 concealed food the following experiments were tried. 



