Figure 7: Transparent vesicle of Dolabrifera dolabrifera ((a)–(e)) and the epidermis of its ink gland ((f) and (g)). ((a) and (b)) The electron-lucent lumen is surrounded by a thin layer of cytoplasm against which electron dense material (arrows) is deposited. ((c)–(e)) Arrays of filaments with translucent cores (arrows in (d)) and a wall composed of subparticles (arrows in (e)) were occasional found free in the vesicle lumen. ((f) and (g)) Cells below the epidermis containing protein (f) or pigment granules (g). c, connective tissue; m, muscle; mv, microvilli; n, nucleus; p, protein granule; pi, pigment granule. Scale bars: (a) and (b) = 1 μm; (c) = 200 nm; (d) and (e) = 50 nm; (f) = 1 μm; (g) = 2 μm.