Fig. 5. Electron microscopy of secretory vesicle types. (A) Unstimulated cement gland where most of the cement granules appear densely packed with secretory material. Granule contents appear to have a distinct organization. Scale bar, 0.6 µm. (B) Type 2 granules appear larger and their contents appear amorphous and lack the organization observed in the dense-core vesicles seen in A. Scale bar, 0.6 µm. (C) Type 3 granules appear similar to type 2, except have a `moth-eaten' appearance with clear spaces or hydration channels due to partial loss of contents. Scale bar, 0.25 µm. (D) Type 4 vesicles appear like vacuoles with a reticulated appearance. Note that the reticulated granules appear within the same cell as the dense-core type 1 granules. Scale bar, 0.4 µm.