140 American Fisheries Society 



(bullhead, dogfish) , they may for a time pay no atten- 

 tion to the packets. If they are fishes that habitually 

 seek food by the use of the eyes (killifish) , they may at 

 first bite at both packets in the same way. But in either 

 case, as the juices from the meat penetrate into the wa- 

 ter, the fish show signs of being stimulated. While the 

 killifish pay little or no heed to the meatless packet they 

 now crowd about that containing meat and bite at it. 

 The dogfish and the bullhead move restlessly about until 

 they finally come into contact with the packet containing 

 the hidden food, when they attempt to seize it. 



Water may be prevented from entering the nasal sac 

 of any of these fishes by closing its anterior opening. 

 This may be done by tying a thread about the opening, 

 by stitching its lips together or by filling it with cotton. 

 Fish thus treated show no difference in their behavior 

 toward packets containing meat and those without it. 

 The killifish, which sees the packets, may bite at either 

 packet, but soon ceases to notice them. The dogfish does 

 not become restless and seek about for food. If the ob- 

 struction is then removed from the opening of the nasal 

 sac, so that water may pass through it, the fish, after 

 resting for a while, recover their power to tell the packet 

 that contains meat from that which does not. It is thus 

 clear that fish are stimulated by substances emanating 

 from the meat and that these substances affect the olfac- 

 tory organ. The sense of smell enables the fish to detect 

 invisible food at a distance. How great the distance may 

 be we do not know. Professor Parker records a state- 

 ment of Mr. Vinal Edwards "that it is the custom in 

 fishing for dogfish to throw out in the tide lines baited 

 with menhaden or alewives. For a time no dogfish will 

 be seen, then they will appear in numbers, swimming 

 around the bait in gradually diminishing circles until 

 finally it is seized." It seems that the dogfish do not see 

 the bait but that they smell it at a considerable distance 

 and that the odorous material carried to them by the 

 water must be very greatly diluted. 



