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Description of Hausmanniella discoideaColpodid ciliate, 50-120 x 40-60 microns. Shape highly variable. Usually slightly obovoid with the anterior often a little broader than posterior, right margin (dorsal side) distinctly convex, left (ventral side) slightly concave at level of oral apparatus, anterior left end sometimes bluntly pointed; such specimens strongly resemble Bryometopus pseudochilodon. Others resemble Avestina ludwigi, as their postoral portion is distinctly narrowed, sometimes even pointed. Flattened about 2-3:1, right side almost flat, left moderately convex and vaulted slightly postorally causing indistinct diagonal groove which is, however, not recognizable in the infraciliature. Macronucleus spherical to slightly ellipsoid, near centre of cell; nucleoli large, spherical to vermiform. Micronucleus not known. Contractile vacuole at ventral side in posterior third of cell. This feature is hard to see in overfed specimens and rather variable in various populations. Cytopyge at posterior end. Cortex colourless, very flexible and fragile, distinctly furrowed by ciliary rows, especially on keel. Within kineties many tiny granules (mucocysts?) which stain red with methyl green-pyronin. Cytoplasm colourless, often crammed with up to 1000 small (2-4 microns) food vacuoles containing bacteria, small ciliates, fungal spores, fungal hyphae or small algae. Slowly to rapidly gliding on surfaces and soil particles. Cilia 8-10 microns long, paired throughout. Somatic kineties spirally coursing, preorally more densely ciliated than postorally, those of right and left side abut preorally to form straight suture slightly left of median. 30-50 dikinetids in 4th somatic kinery right of oral apparatus. Subterminally on right side, right of median, 20-30 ciliated dikinetids spaced very closely both consecutively and side by side. No shortened (vestibular) kineties on right slope of vestibulum. Oral apparatus in anterior half of body. Vestibulum moderately large and only slightly depressed exposing crescentic cytostomial cleft on surface of cell. Pharyngeal fibres short and fine. Left oral polykinetid 8-14 microns long, horizontally orientated, slightly curved, only proximal end covered by right wall of vestibulum, comprises about 17 kineties. Right polykinetid consists of almost completely disordered basal bodies; proximal half slightly twisted, distal portion lengthened semicircularly so far that it sometimes almost touches distal end of left polykinetid (length of "tail" differs slightly in various populations but is always conspicuous).