The Problem of Color Vision in Fishes

Abstract

EV VIDENCE on color vision in fishes is conflicting. Because of the fact that certain fishes rather consistently respond either positively or negatively to light, it has seemed convenient to certain experimenters to use the preference method in the investigation of color vision in these animals. If it could be shown that a fish, repeatedly forced to choose between two lights differing in wave-length only, always or nearly always selected the same one of these lights (position and other variables being controlled), it would seem impossible to deny that the animal was capable of differential response to wavelength. It should be said at once that no investigator has presented conclusive evidence for such behavior. None has satisfactorily controlled the intensity factor. Even Hess, who has taken more pains than have many others, failed at this point. Graber (i9) was perhaps the earliest investigator to use the preference method in an attack on this problem. He found with the freshwater fishes, Cobitus barbatula and Alburnus spectabilis, a preference for the dark rather than the light, for blue without ultraviolet rather than blue with ultraviolet, for red rather than green and for green rather than blue with ultraviolet. The following year (to) he obtained about the same results on the marine forms Gasterosteus spinchia L. and Syngnathus acus L. Furthermore he found that it was possible to reverse the preference for red over blue by using an intensity of the former twenty times as great as that of the latter. Although Graber's work appears to indicate wavelength discrimination it cannot be accepted as anything more than a suggestion because of technical flaws. The colors were produced by pigmented glass and the intensities were equated by using pairs of colors which appeared to be equally bright to the human eye. The source of illumination is not given. Graber described the distribution of the fishes thirty minutes after the beginning of the light stimulation conditions. Hess (z-) criticizes him for not also reporting the immediate responses.