Reighard. — Senses and Learning in Fishes 139 



We have seen that the fish tastes three classes of sub- 

 stances that we also taste : salt, sour and bitter. It fails 

 to respond to one sweet substance that affects our taste 

 organs, sugar. It responds through its organs of taste 

 to one substance for which we have no separate sensa- 

 tion of taste, and, although we do not know what this 

 substance is, we may refer to it as a sapid substance in 

 meat. The fish then tastes one substance that does not 

 affect our organs of taste, and there may be other sub- 

 stances that affect its taste organs, but do not affect our 

 own. We do not then know how many substances a fish 

 tastes. We know only that it responds negatively to salt, 

 sour and bitter and positively to meat. We may there- 

 fore say that it can tell the difference between meat juice 

 and the salt, sour and bitter substances used — but we 

 cannot say that it can tell salt, sour and bitter from each 

 other — for it behaves in the same way toward all of them. 



2. Smell in fishes. The organs of smell in fishes are 

 two small sacs located in the snout, one on either side in 

 front of the eye. In most fishes they lie on the upper 

 side of the snout, but in sharks on the lower side. Each 

 has two openings on top of the head (except in sharks), 

 one in front of the other. A current of water, produced 

 in different ways in different fish, enters the anterior of 

 these openings and passes out through the other. But 

 the sacs do not communicate with the cavity of the mouth 

 so that, unlike man, it is probable that fishes are unable 

 to smell things held in the mouth. 



The sense of smell in fishes has recently been studied 

 in the bullhead, Ameiurus nebulosus (Parker, 1910), in 

 the killifish, Fundulus heteroclitus (Parker, 1910, 1911, 

 1912), in the smooth dogfish, Mnstelus canis (Sheldon, 

 1909, 1911; Parker, 1912; Parker and Sheldon, 1913), 

 and in the puffer (Copeland, 1912). 



The usual method of experiment has been to prepare 

 two packets of cheese cloth, one of which contains meat 

 while the other does not. These are placed in an aqua- 

 rium containing several of the fish. If the fish used are 

 of species that do not ordinarily seek their food by sight 



