THE DIFFERING EFFECTS OF DIFFERENT PARTS OF THE VISUAL FIELD UPON THE CHROMATOPHORE RESPONSES OF FISHES

Publisher Website
Google Scholar
Abstract
(1) Darkening the lower half of the field of vision by the insertion of false corneas of celloidin resulted in a pronounced darkening of the entire dorsal surface of the fish (Fundulus parvipinnis), even when the animal was kept upon a white background. (2) Darkening of the upper half resulted in no visible change (unless a slight darkening) when the fish was on white, but a fish so treated was commonly considerably paler than a control when placed upon a dark gray background. This fact, along with that stated in the preceding paragraph, seems to support the view that the shade which a fish assumes upon a given background is determined by the relative luminosity of the upper and lower portions of the visual field, the latter acting in a positive sense, the former in a negative. (3) Various other stimuli, optical and otherwise, were found to affect the shade assumed by the fish, and these greatly complicated the interpretation of the experiments. (4) Covering both eyes with opaque "blinders" resulted in the assumption of an intermediate shade. Contrary to the findings of von Frisch with the trout, the covering of one eye, in a fish kept on a white background, resulted in only a slight darkening. Furthermore, no trace of asymmetrical chromatophore response on the body was noted, following asymmetrical optical stimulation. (5) In experiments during the winter and early spring, it was found that transparent "corneas" which were stained yellow, either throughout their entire extent, or in the lower half only, led to the assumption of a distinctly yellowish hue by the fish. In another series, some months later in the year, little evidence of such color changes was found. This accorded with the fact that these fishes responded markedly to yellow backgrounds during the earlier months, and ceased to do so during the later ones. Some physiological change of a seasonal nature appears to be involved here. (6) Besides yellow, and to a lesser degree red, no other color evoked any specific color responses on the part of the fish. On the contrary, various color changes were manifest which obviously bore no relation to the chromatic stimuli.