The development of the retinotectal projection in Xenopus with one compound eye

Double-nasal and double-temporal compound eyes were constructed in Xenopus embryos at stages 32 and 37/38. A particular half was removed from the host eye anlage and replaced with the opposite half-eye from the contralateral side of a donor embryo. Control operations consisted of removing a half-eye and replacing it with a similar half from the ipsilateral side of the donor embryo. Whereas in control animals, each half-eye projects its fibres to the appropriate half-tectum, in operated animals each half of the compound eye spread its optic terminals across the entire rostrocaudal extent of the dorsal tectal surface. The area of tectal surface covered by ganglion fibre terminals was similar in operated animals mapped at successive stages of development to that previously observed in normal animals at equivalent stages. Therefore the factors responsible for the extended distribution of fibre terminals from each half of a compound eye must exist at least from mid-tadpole life, and thereafter be continuously present throughout development.