The innervation of a virgin tectum by a double-temporal or a double-nasal eye in Xenopus.

In Xenopus embryos at stage 32/33 one eye anlage was removed and the other made into a compound double-nasal or double-temporal eye. At metamorphosis the optic nerve was cut and the compound eye was permitted to regenerate fibres both to its own contralateral tectum and to the ipsilateral 'virgin' tectum. One month later the projection from the compound eye to the virgin tectum was assessed autoradiographically by use of tritiated proline. Projections from double-temporal eyes were found to be restricted to rostrolateral tectum, whereas projections from double-nasal eyes covered the entire tectal surface. It was concluded that the results did not suggest that positional markers existed on the tectum before the arrival of the optic fibres.