The retinotectal fibre pathways from normal and compound eyes in Xenopus

Horseradish peroxidase was used to demonstrate the nature of the retinotectal fibre pathways from normal eyes and from compound double nasal (NN), double temporal (TT) and double ventral (VV) eyes in Xenopus. From normal eyes, nasal fibres were widespread in the optic tract and mostly entered the tectum through the medial and lateral brachia. Ventral retinal fibres approached the tectum via the medial brachium and dorsal retinal fibres passed through the lateral brachium, while temporal retinal fibres formed a narrow band in the centre of the tract and entered the tectum directly at its rostral border. Fibres from NN eyes formed a wide tract and strong medial and lateral brachia. Fibres from VV eyes all entered the tectum via the medial brachium and fibres from TT eyes formed a narrow tract and entered the tectum directly from its rostral extremity. Thus fibres from each type of compound eye followed pathways to the tectum that were appropriate to the embryonic origin of the retina forming the compound eye.