THE DIFFERENTIATION OF THE EPIDERMIS IN RANA PIPIENS

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Abstract
The development of the skin was studied in tails of tadpoles of Rana pipiens, varying in length from 3 mm to 24 mm. Attention was directed to the cytogenesis of the component cells and to the nature and differentiation of the contact between cells and of the basement lamella. The epidermis is two layered and there are distinct cytological differences between the cells of the apical and basal layers. The basal cells develop considerable endoplasmic reticulum and acquire numerous tonofilaments. Desmosomes, with which some of the tonofilaments are associated, make their appearance in the 8 mm stage and become more numerous in succeeding stages. The nature of the dermo-epidermal junction in successive stages is described, up to the appearance of a typical basement lamella in the 24 mm stage. The complexity of this lamella is indicated and theories concerning the origin of the component fibrillae are discussed.