The retinotectal projection of quarter eyes in Xenopus laevis.

Following extirpation of three quarters of the eye anlage of Xenopus laevis in stage 33/34, the remaining quadrants developed into small eyes of normal shape. Irrespective of the different portions of the eye anlage the quarter eyes originated from, the retinotectal projection was always confined to the rostrolateral part of the tectum, forming an orderly map, and its dimensions corresponded to the size of the contralateral eye. Therefore, it was suggested that during development both size and location of the projection are independent of the existence of tectal markers. Instead, they are determined by the number of ingrowing optic fibers and the direction of their growth from the rostral origin.