Development of the dermis (1): embryonic stages. Extracellular material giving rise to the dermis is shown accumulating between the epidermal and mesendodermal cells during embryonic stages. In all panels, ectoderm is to the left, mesendoderm (A, B) or somitic mesoderm in (C-F) is to the right. (A) shows an overview, and (B) is a detail showing particulate extracellular material associated with both cell layers (arrow indicates matrix outside the epidermal cell in B, C). White arrowheads in (D) and (F) indicate clathrin-coated vesicles observed in both epidermis and mesoderm. Black arrowhead in (F) indicates the basal lamina formed by the end of embryogenesis. Images are to scale except A (as indicated), and all sections are transverse; dorsal is up, lateral to the left and medial to the right. Stage abbreviations: gast, gastrula; neur, neurula.