The Development of Phototaxis in the Frog (Rana Temporaria)

Abstract

1. The development of phototaxis in the frog was studied by testing the behaviour of tadpoles at different stages of their development. The development of the retina at each stage was checked from histological preparations. 2. Young tadpoles responded most strongly to green light (approx. 550 mµ). Gradually the number of responses to green light decreased, while more responses were made to blue light, and also to darkness. Adult frogs respond most strongly to blue light; light of wavelengths longer than about 510 mµ is responded to only slightly more often than darkness. 3. It was concluded that the phototactic behaviour of frogs is probably mediated by a synergistic action of the green rods and the cones, which have an excitatory effect, and which are opposed by an inhibitory effect of the red rods.