Eye-specific termination bands in tecta of three-eyed frogs.

An extra eye primordium was implanted into the forebrain region of embryonic Rana pipiens. During development both normal and supernumerary optic tracts terminated within a single, previously uninnervated tectal lobe. Autoradiographic tracing of either the normal or supernumerary eye's projection revealed distinct, eye-specific bands of radioactivity running rostrocaudally through the dually innervated tectum. Interactions among axons of retinal ganglion cells, possibly mediated through tectal neurons, must be invoked to explain this stereotyped disruption of the normally continuous retinal termination pattern.