Olfactory Reactions in Fishes 5^9 



and the other wad were interchanged in position. Not only 

 did the fishes thus openly seize this wad, but, when in its neigh- 

 borhood, they would often turn sharply as though seeking some- 

 thing but without success, a form of reaction seldom observed 

 near the wad which contained no worms. Two other sets, of five 

 normal fishes, each, were tested in this manner and with similar 

 results. It was perfectly clear to anyone watching these reac- 

 tions that the fishes sensed the difference between the wad of 

 cloth with worms and that v/ithout worms. 



To ascertain what receptive organs were concerned in the re- 

 actions just described, I took from among the fifteen normal fishes 

 already tested two sets of five each and prepared each set differ- 

 ently by subjecting its members to a special operation. One set 

 was etherized, and, through a small incision between the eyes, 

 their olfactory tracts were cut thus rendering their peripheral ol- 

 factory apparatus functionless. From fishes of the other set all 

 the barblets were removed whereby their external gustatory or- 

 gans were partly, though not v^holly, eliminated. After these 

 operations both sets of fishes were liberated in the large aquarium 

 where they remained for over two days. At the expiration of this 

 time, thev were carefully inspected and tested. They swam about 

 in an essentially normal way and members of both sets snapped 

 bits of worm Irom the end of a hooked wire much as a normal fish 

 does. I therefore judged them to be m a satisfactory condition for 

 experimentation. 



The tests were begun by introducing into the large aquarium 

 containing the ten fishes a wad of cheese-cloth within which were 

 hidden some minced earthv/orns and recording the kind of fish 

 that visited it and the nature of their reactions. During the 

 first hour the wad was seized 34 times by fishes without barblets 

 but with normal olfactory organs and, though often passed by 

 fishes with cut olfactory tracts, it was "nosed" only once by one 

 of these . I next substituted a Vv'ad of cheese-cloth without worms 

 for that with worms and recorded the reactions of the fishes for a 

 second hour. Though members of both sets frequently swam by 

 this wad, none at any time during the hour seized it or even 

 nosed it. These tests were repeated on the same fishes for two sue- 



