The growth of the chick retina after hatching.

In autoradiographs of the retina from two-week old chicks injected with tritiated thymidine during the first week after hatching, the labelled cells were found mainly in the extreme periphery of the retina and the ciliary epithelium of the pars plana. The pattern of labelling in the extreme periphery resembles that observed (Fujita and Horii, '63) in retinae exposed to tritiated thymidine during embryonic development. The mechanisms underlying the histogenesis of retinal cells during growth at the extreme periphery in young stages may be the same as those which operate during embryonic devolopment.