Summary of Ablation and Cell Movements. (A) A large anterior ablation (scissors and shaded area) that includes the area giving rise to the rod free zone (red dot) is healed by the movement of cells along the anterior/posterior axis (large blue arrow), with little contribution from the dorsal/ventral regions (small blue arrow). In this experiment, the rod free zone is lost and the cells that would normally reside more centrally are located in the far nasal periphery, which corresponds to the anterior optic vesicle. (B) A large posterior ablation (scissors and shaded area), which does not include the rod free zone (red dot) is healed by the incorporation of cells from central and anterior regions along the anterior posterior axis (large blue arrow), with little contribution from the dorsal/ventral axis (small blue arrows). In this experiment the rod free zone remains and the retina has acquired an anterior identity.