﻿84 BLIND VERTEBRATES AND THEIR EYES. 



before it came in contact with the lips. Once when I was feeding them meat, the thread touched 

 the lips of one of the fishes. It immediately snapped at the thread. Before I could bring the meat 

 in contact with the Hps, it snapped at the thread a second time. This seemed to indicate that they 

 do not readily distinguish between edible and non-edible substances. Again, I lowered a pair of 

 forceps into an aquarium where there were 15 fishes. All of them were attracted by the disturbance 

 in the water. Fishes 18 indies away turned and swam in the direction of the forceps. I kept the 

 forceps moving just enough to create slight vibrations in the water. Every fish came up and snapped 

 at the forceps and some of them snapped 2 and 3 times. At the least disturbance on the surface 

 of the water these fishes would swim upward as if e.xpecting something to eat. They are able to 

 follow the disturbance anywhere about the aquarium and do it quickly and accurately, turning at 

 any sort of an angle. This experiment was made with non-edible objects, so taste and smell could 

 have played no part whatever. The tactile organs remain as the only means by which these vibra- 

 tions were detected, located, and followed. 



I suspended pieces of fresh beef in the aquarium to see whether the fishes were able to locate 

 it while it remained stationary, but in no case did they pay any attention to the beef. .A.fter I had 

 placed the fishes in the light in individual jars, I had no trouble to get the larger ones to take meat 

 from the end of a thread. I also fastened bits of absorbent cotton to the thread as I had done with 

 the meat, and at first they took the cotton just as readily as they had the meat. The cotton was not 

 swallowed, but ejected as soon as taken into the mouth. The fishes turned if any part of the body 

 was touched, but never snapped until the cotton or meat came in contact with the lips. How- 

 ever, after a few trials with the cotton the snap was not so vigorous, and if continued, the cotton was 

 refused altogether. In the course of 4 hours, I got one fish to take the cotton 1 1 times, but after 

 that it seemed to be able to perceive the difierence and though I kept this individual several months 

 no amount of persuasion could induce it to take another piece of cotton. After this it acted toward 

 the cotton just as it did toward the beef until the cotton came in contact with the lips, when it would 

 refuse it. I did get it to take cotton soaked in beef juice. I tried 2 fishes by placing bits of meat on 

 the bottom of the aquarium. In swimming close to the bottom, the meat touched the ventral sur- 

 face of the body or the pectoral fins. In each case, the fishes stopped, backed up a little until the 

 lips touched the meat, and then snapped at it. This seems to indicate that this species might, in 

 some cases, take food which was not in motion and that it might locate its food partly by taste. 

 I tried these fishes with cotton in the same manner as I had done with the meat, and they reacted in 

 exactly the same way until the cotton touched the lips, when they refused to take it. One fish did 

 snap up one piece of cotton. 



I also tested their ability to taste by squirting beef juice on various parts of the body. I got no 

 reaction that I could not get with pure water. I dropped beef juice, a drop at a time, on the surface 

 of the water. The fishes were attracted by the vibrations, came to the surface, and snapped at the 

 dro]), but they also reacted in the same manner toward drops of water. They are not able to locate 

 the center of disturlmnce as readily when the drop falls behind them as when it falls on the side or 

 in front. This experiment again shows how sensitive these fishes are to vibrations in the water and 

 how accurately they are able to locate them. 



I might add that slight disturbances, such as the dropping of amphipods into the water, often 

 cause the fishes to sink gradually to the bottom and remain (|uietfor several seconds, after which 

 they begin to swim slowly about. At this time the swimming is accompUshed mostly by the use of 

 the pectoral fins. By a backward stroke, the fins are brought against the body, and then, as the fish 

 glides forward, they are allowed to float out at right angles to the body, the filamentous edge dragging 

 on the bottom. We might term this the "seeking reaction." Amphijiods which touch the fins 

 or any other part of the body at this time are snapped up immediately. 



I mentioned before that the fishes were confined to the quiet pools. It seems to me that their 

 manner of getting food accounts, in part, for their habitat. They eat living animals, and these ani- 

 mals are found by the vibrations which they make in swimming. In running water the fishes could 

 not detect these vibrations. 



A few observations on the memory of Amhlyopsis may be placed on record in this connection. 

 When the fishes are first brought into the laboratory, they are very sensitive to mechanical stimuli. 

 If kept in a place where they are constantly subjected to stimuh, they soon pay much less attention 

 to them. I kept some fishes in battery jars on my table. At first, when I struck the table lightly, 

 they always responded by sj)ringing upward. After a few weeks they responded much less often, 

 and after several months they paid very little attention to jarring of any kind. 



