Retinodiencephalic projections from compound eyes in Xenopus

The contralateral diencephalic projections from compound eyes, made by the early embryonic fusion of two nasal (NN), two temporal (TT) or two ventral (VV) retinal fragments, have been studied in young toads using [(3)H] proline autoradiography. After intraocular isotope injection into compound eyes which represent only half of the normal naso-temporal or dorso-ventral sets of ganglion cells, the total projection to the nucleus of Bellonci (NB), corpus geniculatum thalamicum (CGT) and pretectal nucleus (PN) was found to be the same as in normal eyes. These results show the spreading of a half-retinal projection to the whole of the diencephalic visual centres, indicating that the pattern of retinodiencephalic projections may be modified during embryogenesis.