THE BLIND-FISHES. I i 5 



Bright sunlight appears to be irritating; if exposed to it, the 

 fishes swim about uneasily. A shadow passed suddenly across 

 them, when in the diffuse light of a room, does not affect them ; 

 nor did they seem disturbed, when swimming through a ray of 

 light entering the dark chamber by a small hole in the paint 

 made for the experiment. 



Two examples kept in a pail in my cellar were quietly float- 

 insf, but when a lighted match was held above them, the fishes 

 at once darted to the bottom and sides of the pail. The heat, 

 in this case, could not have been a factor; the reaction to the 

 light of the match was quick and violent. The same observa- 

 tion was made on forty individuals in two aquaria. They were 

 captured one morning, and the observation made the second 

 night after. They had been kept in the dark during most of 

 the intervening time. A lighted match, held near the aquaria, 

 produced a very general and active movement among all the 

 individuals. 



A series of observations was made to determine to what rays, 

 if any, they reacted most vigorously. Only the concluding data 

 need be given here. 



For this experiment a glass jar, three feet long and eight 

 inches in diameter, was divided into six compartments by five 

 partitions. Each partition had a vertical slit extending half- 

 way up from the bottom to enable the fish to swim freely from 

 one compartment to another. The compartments were thus 

 all connected. A cap was screwed tightly over the end of the 

 jar, which was placed horizontally on a window sill where each 

 compartment would have an equal amount of light. The jar 

 was surrounded with bands of tissue paper in several layers of 

 violet, blue, green, orange, and pink, so that each compartment 

 was lighted by one series of rays. 



Three blind-fishes were used for these observations ; they were 

 selected for their size, and numbered : i, the smallest ; 2, the 

 middle-sized ; 3, the largest. These fish had been in confine- 

 ment some time, but had been transferred from the cave, with 

 as little exposure to light as possible, to a dark room, where 

 they were very seldom exposed to the light. 



It was found that certain compartments were visited by a 



