﻿90 BLIND VERTEBRATES AND THEIR EYES. 



Mr. F. Payne has made further studies and found that their negative heliotro- 

 pism is sufficient to overcome their positive geotropism if an 800 candle-power arc 

 lamp is used 16 inches from the aquarium. He also found that the young fish 

 to an inch in length react more strongly to light than older ones, even if their eyes 

 are destroyed, and that one part of the body is as sensitive as another to a pencil of 

 strong light. 



The 7 blinded chologasters mentioned previously were placed at 9 a.m. in an 

 aquarium which was dark at one end and light at the other, but with no partition 

 between. In the bottom of this aquarium, extending from the lighted into the 

 darkened area, was placed a plate of glass propped up at one edge so as to enable 

 the fishes to get under it. The conditions in the two parts of the aquarium were 

 as nearly alike as possible except as to light. The blinded chologasters collected 

 in the darkened half of the acjuarium and remained there. The reaction was quite 

 positive. No sunlight entered the aquarium — only the diffuse light of the room. 

 The same reaction took place when sunlight entered the aquarium. 



Later, the pane of glass was taken from the bottom of the aquarium and placed 

 against its sides, and the fishes collected beliind it in the dark end. A number of 

 normal chologasters in another aquarium had the same habit of squeezing them- 

 selves in between the sides of the box in which they were and the small glass 

 acjuarium placed in it. It is evident that Chologaskr is also negatively helio- 

 tropic and positively stereotropic. 



A series of observations was made to determine to what rays, if any, Amhlyopsis 

 reacts most vigorously. For this experiment a glass jar 3 feet long and 8 inches in 

 diameter was divided into 6 compartments by 5 partitions. Each partition had a ver- 

 tical slit extending half-way up from the bottom to enable the fishes 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 in a 

 vdndow-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 comi)artment was lighted by one series of rays. 

 Three Amhlyopsis were used for these observations ; they were selected for their 

 size and named, A, the smallest, b, the middle-sized, c, the largest. These fishes 

 had been in confinement some time, but had been transferred from the cave, with 

 as little exposure to light as possible, to a dark rooni where they were very seldom 

 exposed to the light. Observations were made as o]i]x)rtunity presented itself. 



It was found that some compartments were visited by a certain fish without any 

 definite regard for color. During January, for instance, fish c moved out of the jiink 

 and orange compartments but once ; fish A remained almost exclusively in yellow, 

 \isiting pink once, orange once, and green 4 times. Fish b, on the other hand, 

 remained mostly in the violet, visiting blue 7 times and gi-cen 3 times. From this 

 we must conclude either tliat different individuals react differently or that one color 

 does not produce a stronger reaction than another, and the latter seems the more 

 reasonable conclusion. (See table on page 91.) 



To determine whether the apparatus had anything to do with the distribution 

 and also whether widely separated elements of the spectrum would cause the fishes 



' For over a month these fishes were sealed in this j.ir without change of water. 



