A favorable view of one trichocyst docking site in a quick-freeze deep-etch image shows the prominent outer ring of 37 IMPs and about the same number of IMPs in the inner ring more deeply embedded in the cytosolic leaflet. Pits, where the rosette was removed during fracturing of the chemically-unfixed rapid-frozen cell, are seen at the center of the docking site. Two gaps in the rings indicate the site of the septum in the underlying alveoli where the plasma membrane is not linked to the alveolar rims by the ring IMPs. TEM taken on 2/15/90 by R. Allen with Zeiss 10A operating at 80kV. Neg. 31,500X. Bar = 0.2µm.