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forms, such as peritrichs , suctorians , 
and chonotrichs . Using similarities in division mor-
phogenesis and an imagined evolutionary trans-
formation from hymenostome to thigmotrich to 
peritrich, Fauré-Fremiet (1950a) made the case 
for the “ hymenostome ” affinities of the peritrichs 
(Fig. 1.1). His student, Guilcher (1951), argued 
that suctorians and chonotrichs ought not to be 
1.2 The Age of the Infraciliature (1950–1970) 3
Fig. 1.1. A Schematic drawings of the hymenostome Tetrahymena, the thigmotrich Boveria, and the peritrich 
Vorticella. Fauré-Fremiet (1950a) related these three groups in a transformation series, imagining that evolution of 
the peritrich form proceeded through a thigmotrich-like intermediate from an ancestral Tetrahymena-like hymenos-
tome. B Schematic drawings of the cyrtophorine Chilodonella and of the mature form and the bud of the chonotrich 
Spirochona. Guilcher (1951) argued that the similarities in pattern between the chonotrich bud and the free-living 
cyrtophorine suggested a much closer phylogenetic relationship between these two groups although the classification 
scheme of Kahl suggested otherwise (see Table 1.1)
4 1. Introduction and Progress in the Last Half Century
greatly separated from other ciliate groups, and she 
claimed that chonotrichs might in fact be highly 
derived cyrtophorine gymnostomes (Fig. 1.1). 
 Furgason (1940) in his studies of Tetrahymena
had imagined a more global evolutionary transfor-
mation of the oral apparatus of ciliates, premissed 
on the assumption that the three membranelles or 
oral polykinetids of Tetrahymena and the hymenos-
tomes preceded the evolution of the many mem-
branelles of the heterotrichs , like Stentor (Fig. 1.2).
 This view was supported by Fauré-Fremiet 
(1950a) and Corliss (1956, 1961) who envisioned 
the hymenostomes as a pivotal group in the evo-
lutionary diversification of the phylum. Corliss 
(1958a) used this concept of transformation of 
oral structures from simpler to more complex to 
argue that the hymenostomes , in their turn, had 
their ancestry in “ gymnostome ”-like forms, such as 
the nassophorean Pseudomicrothorax , which itself 
became another pivotal ancestral type. This led to 
the rearrangement of higher taxa and the proposal 
of a “Faurean” classification system by Corliss 
(1961) (Table 1.2). 
 This new view still maintained the Holotricha 
and Spirotricha , but the opalinids had now been 
removed based on the recognition that they shared 
many significant features with flagellate groups 
(Corliss, 1955, 1960a). Considering the work of 
the French ciliatologists, Corliss (1961) transferred 
the peritrichs , suctorians , and chonotrichs into the 
 Holotricha , recognizing their probable ancestry 
from groups placed in this subclass. Oral structures 
continued to play a dominant role in characterizing 
orders as indicated by the common suffix “-stomatida” 
(Table 1.2). 
 Of course, the underlying assumption of the 
transformation of oral structures proposed by Fauré-
Fremiet, Furgason, Corliss, and others was that the 
oral polykinetids or membranelles of these differ-
ent ciliates – Pseudomicrothorax , Tetrahymena , 
and Stentor – were homologous. It was the inven-
tion of the electron microscope, which was just 
beginning to demonstrate its applicability during 
the latter part of this period, that was to provide the 
evidence to refute this assumption and therefore 
undercut the general application of this concept. 
Fig. 1.2. Schematic drawings of three ciliates that have multiple oral polykinetids. The hymenostome Tetrahymena
has three oral polykinetids and a paroral while the spirotrich Protocruzia and the heterotrich Stentor have many more 
than three. Furgason (1940) imagined that evolution proceeded by proliferation of oral polykinetids or membranelles 
and so the major groups of ciliates could be ordered by this conceptual view into more ancestral-like and more 
 1.3 The Age of Ultrastructure 
 As with other ages, the technological roots of 
the Age of Ultrastructure began in the 1950s and 
1960s. The silver proteinate staining technique of 
Bodian or protargol staining became established 
as the light microscopic stain of choice during this 
period, although it had its technological innova-
tors in the previous age (Kozloff, 1946; Kirby, 
1950; Tuffrau, 1967). However, it was electron 
microscopy, promoted by Pitelka (1969), that 
gained preference in resolving questions in both 
the systematics and cell biology of ciliates. These 
early results, coupled with two seminal papers by 
1.3 The Age of Ultrastructure (1970–1990) 5
Table 1.2. Faurean classification and post-Faurean system adopted by Corliss (1979).a
Faurean Era (1950–1970) Post-Faurean Era (1970–1981)
Subphylum Ciliophora Phylum Ciliophora
Holotricha Gymnostomata Hymenostomata
Gymnostomatida Primociliatida Hymenostomatida
 Rhabdophorina Karyorelictida Tetrahymenina
 Cyrtophorina Prostomatida Ophryoglenina
Suctorida Archistomatina Peniculina
Chonotrichida Prostomatina Scuticociliatida
Trichostomatida Prorodontina Philasterina
Hymenostomatida Haptorida Pleuronematina
 Tetrahymenina Pleurostomatida Thigmotrichina
 Peniculina Vestibulifera Astomatida
 Pleuronematina Trichostomatida Peritricha
Astomatida Trichostomatina Peritrichida
Apostomatida Blepharocorythina Sessilina
Thigmotrichida Entodiniomorphida Mobilina
 Arhynchodina Colpodida POLYHYMENOPHORA
 Rhynchodina Hypostomata Spirotricha
Peritrichida Synhymeniida Heterotrichida
 Sessilina Nassulida Heterotrichina
 Mobilina Nassulina Clevelandellina
Spirotricha Microthoracina Armophorina
Heterotrichida Cyrtophorida Coliphorina
 Heterotrichina Chlamydodontina Plagiotomina
 Licnophorina Dysteriina Licnophorina
Oligotrichida Hypocomatina Odontostomatida
Tintinnida Chonotrichida Oligotrichida
Entodiniomorphida Exogemmina Oligotrichina
Odontostomatida Cryptogemmina Tintinnina
Hypotrichida Rhynchodida Hypotrichida
 Stichotrichina Apostomatida Stichotrichina
 Sporadotrichina Apostomatina Sporadotrichina
 Classes are indicated in bold capital letters; subclasses, in italics; orders, in bold with the ending 
“−ida”; suborders, further indented with the ending “−ina”.
6 1. Introduction and Progress in the Last Half Century
Jankowski (1967a, 1973c), prompted the French 
group of de Puytorac, Batisse, Bohatier, Corliss, 
Deroux, Didier, et al. (1974b) and, both with 
his French colleagues and independently, Corliss 
(1974a, 1974b) to propose revised classifications. 
Corliss (1979) used a slightly modified version in 
his third edition to “The Ciliated Protozoa” (Table 
1.2). About this time, Jankowski (1980) proposed 
a new system, which still placed major emphasis 
on oral features as indicated by the names of some 
of his classes – Apicostomata , Pleurostomata , 
 Rimostomata , Synciliostomata , Cyrtostomata , and 
 Hymenostomata . 
 The major feature of these post-Faurean schemes 
was the prominent elevation of oral features. The 
three classes in the phylum were now character-
ized by the nature of the oral apparatus: small, 
simple kinetal fragments characterized the Class 
 Kinetofragminophora ; typically three oral poly-
kinetids or membranelles characterized the Class 
 Oligohymenophora ; and many more than three mem-
branelles characterized the Class Polyhymenophora
(Table 1.2). All three names derived from the 
conceptual vision of Jankowski (1967a, 1973c, 
1975), which shared the same assumption as 
Furgason’s: homology was assumed among “oligo”-
membranelles and “poly”-membranelles. 
 Before we return to a refutation of this assump-
tion, it is