Figs 6–12.

Maryna umbrellata, resting cysts in the light microscope (6, 8, 10–12) and in the SEM (7, 9). 6, 10 – overview and detail, showing that most of the thick mesocyst is covered by the opaque pericyst composed mainly of glass granules. The cysts are studded with “spongy globules”; 7, 9, 12 – the cyst surface is coarse and may be more or less facetted (7). At higher magnification, the pericyst is composed of countless silicon granules (7b, 12) embedded in mucous material, which becomes distinct where the granules have been lost (9, asterisk); 8, 11 – squashed cysts showing the thick, split mesocyst (arrows), the thin endocyst (opposed arrowheads), and the glass layer. The asterisk marks the ectocyst and the basal layer. B – bacterial rod, E – endocyst, G – glass granules in mucous cover, L – lipid droplets, M – mesocyst, MA – macronucleus, MC – mucous cover, P – pericyst, SG – spongy globules. Scale bars: 2 μm (Figs 9, 12), 5 μm (7a), 10 μm (10, 11), and 40 μm (6–8).