Reighard. — Senses and Learning in Fishes 141 



When a dogfish seeks hidden food in an aquarium it 

 seems to circle about in a restless, random way until it 

 finally comes upon the food by chance. Its sense of smell 

 does not seem to direct it to the food. But Professor 

 Parker found that if one nasal sac of a dogfish was filled 

 with cotton and the other left open — the fish in seeking 

 food, turned more often in the direction of the open 

 sac. It thus became clear that the nasal organs do more 

 than make the fish aware of the presence of food in its 

 neighborhood; they guide the fish toward unseen food. 

 The fish turns toward that side from which the stronger 

 odor comes out and thus finds the food more quickly. 



On the whole the organs of smell in fish serve the same 

 purpose as in man. In both they are sensitive to very 

 minute quantities of substances emanating from distant 

 bodies and not only make the animal aware of the pres- 

 ence of these bodies but direct its course to them. In 

 the fish, as in man, there are probably very many sub- 

 stances that affect the organs of smell. 



3. The need of taste and odor in baits. The fisher- 

 man who would know the use made by the fish of the 

 senses of touch, taste and smell in taking bait, must dis- 

 tinguish two classes of fish. Those that are guided to 

 their food by sight and feed by day may take into the 

 mouth anything of suitable size that attracts attention 

 by its movement. The fish then tastes the bait, and it 

 may be rejected if the taste is not satisfactory and if the 

 fish is not at once hooked. If fish of this group are not 

 to be hooked immediately, if they are to be given time 

 to run with the bait, it seems clear that the bait should 

 not be merely salt, sour or bitter, for these repel the fish. 

 It should contain some "sapid" juice like that of meat. 



If the fish do not feed by sight or if the fishing is done 

 at night then again bait should contain some sapid sub- 

 stance that the fish may taste it. It will be more effec- 

 tive if it has also odor. When such odorous bait is put 

 into the water the fish are directed to it by the sense of 

 smell, even in the dark. If they come into contact with 

 it with any part of the body containing taste buds they 



