Fig. 5. Ultrastructure of homotypic and heterotypic septate junctions in the ectoderm of a heterograft (24 h old). (A) The left and the right white arrowheads show homotypic junctions between two cells of H. oligactis (o), enlarged in (B), and two cells of H. vulgaris (v), enlarged in (D), respectively. Note the regular septae and spaces between cell membranes. (C) Enlargement of the heterotypic junction indicated by the black arrowhead in A. White arrows in A point to the heterotypic contact with a few irregular septae and spaces between cell membranes shown in C. g, glycocalyx. Note the species-specific differences in thickness of glycocalyx. Scale bars, 0.5 µm.