Figure 1 in The search finds an end: the morphologically chimeric hysterocinetids belong to the subclass Hymenostomatia (Ciliophora: Oligohymenophorea)

Figure 1. Protoptychostomum simplex in vivo (A) and asser protargol impregnation (B–I). A, less-side view of a representative specimen. B, F–I, less-side overviews, showing the variability of body shape and size as well as of the nuclear apparatus (shaded grey) and sucker (shaded yellow). Dashed circles in (I) represent contractile vacuoles. C, oral ciliary paưern. The paroral membrane and both membranelles extend along the whole posterior body end to plunge into the infundibulum where they form a helix-like paưern. Membranelle M1 is made up of two rows of basal bodies and is not segmented. Membranelle M2 runs beside M1, is composed of only a single row of basal bodies and is not segmented. Arrowhead in (C) marks the curved anterior end of membranelles M1 and M2. D, E, ciliary paưern of the less (D) and the right (E) side. CP, cytopharynx; CV, contractile vacuoles; M1–2, membranelle 1 and 2; MA, macronucleus; MI, micronuclei; PM, paroral membrane; S, sucker; SK, somatic kineties. Scale bars = 30 µm (I), 40 µm (A, B, D, E), 80 µm (H), 100 µm (F, G).