Images of somatic ACT1Δ transformants, immunostained with anticentrin monoclonal antibody 20H5 (A to F and H to I) or polyclonal antitubulin antibody (G). “Left” and “right” refer to the cell's left and right, which is opposite to the viewer's left and right, except in E. (A) A predividing cell with compound ciliary structures of the anterior oral apparatus (OA) and the posterior oral primordium (OP) located along the same longitudinal meridian. Ciliary rows (CR) with basal bodies (BB) are equatorially subdivided to make up a fission zone (FZ), the site of the future division furrow. (B) An optical cross section of a divider in an early stage of reintegration. The division furrow (DF), oral apparatuses (OA1 and OA2), and divided macronuclei (Mac1 and Mac2) are visible. (C) A more fully reintegrated ex-divider (DF, regressed division furrow) with a fully formed oral crescent (OC) of the posterior oral apparatus (OA2) and lateral displacement of OA2 relative to its anterior counterpart (OA1). The presumptive anterior daughter cell possesses a normal anterior crown of basal body couplets (AC1), whereas the anterior end of the posterior daughter cell has only a few brightly stained developing anterior basal body couplets (dAC2). (D) One surface of a partially reintegrated former divider. One ciliary row of the posterior presumptive daughter cell (marked with an arrowhead at its posterior end) appears to be continuous with a ciliary row of the anterior daughter cell. (E) The opposite surface of the same cell as in D. About eight ciliary rows of the posterior daughter cell have formed a partial anterior crown of basal body couplets (AC2). (F) A more completely reintegrated former divider with three ciliary rows (marked a, b, and c) secondarily rejoined across the former fission zone. Other ciliary rows (arrow) have become disrupted and fragmented near the fission zone. (G) Antitubulin staining of a reintegrated cell. OA2 is on the viewer's left side of the cell, and OA1 is on the opposite cell surface and therefore is not visible in this section. Ciliary basal bodies (BB) are indistinctly visible, with prominent longitudinal microtubule bands (LM) immediately to their right, and transverse microtubule bands (TM) extending to their left. Cilia (C), some detached from their cellular moorings, are brightly stained. The LMs on two ciliary rows (marked c and d) appear to be continuous across the former fission zone, and those on a third (marked e) have a small equatorial gap (arrow). Two other ciliary rows, marked a and b, are laterally offset at the fission zone. (H) A failed divider that has attempted to divide again. The less distorted posterior fission zone (arrow) is likely to be the more recent one. (I) An irregular monster representing the end state of successive aborted divisions. An oral apparatus (arrow) has normal membranelles, undulating membrane, and an oral crescent. Bar, 10 μm.