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[Differentiation of the retina and pigment epithelium in the ontogeny of the common frog. 2. Pigment epithelium].

Changes in the differentiating pigment epithelium cells have been studied in Rana temporaria by transmission electron microscopy. Ultrastructural features of the pigment epithelium functions at successive developmental stages have been established: the phagocytic function appears the first (judging by utilization of embryonic pigment from the primary eye cavity), it is followed by the transport and barrier functions (as the secondary eye cavity and vascular envelope develop), while phagocytosis related to the process of renovation of the external segments of photoreceptors and the function of screening appear later.