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heavily armed with 
toxicysts , and – though ciliated and active – it is not 
capable of effecting extreme changes in its length; 
the non-homologous “proboscis” of Didinium is that 
organism’s everted cytopharyngeal apparatus . 
Protargol : see Silver Impregnation Techniques . 
Proter : anterior filial product of a regular binary 
fission of the parental form ; the posterior daughter 
is the opisthe (Fig. 2.11Aa). 
Protolorica : (pl. Protoloricae ): lorica constructed 
by the proter of tintinnid spirotrichs after cytokine-
sis ; see Epilorica and Paralorica . 
Protomite : relatively brief stage in the polymorphic 
life cycle of a few ciliates (e.g., some apostomes ), 
recognizable by features of its kinetome as a sepa-
rate form between the tomont and the tomite . 
Protomont : relatively brief stage in the polymor-
phic life cycle of a few ciliates (e.g., some apostomes ), 
recognizable by features of its kinetome as a 
separate form between the feeding trophont and the 
often encysted true tomont . 
Protrichocyst : older, once popular term for muco-
cyst ; a stage in the development of a trichocyst. 
Psammophilic : literally “sand-loving”; descriptive 
term for interstitial forms found in, on or at least 
temporarily associated with, the sands of intertidal 
zones in marine littoral biotopes or in fresh-water 
beaches and the like. 
Pseudobuccal Kinety (pl. Kineties ): an oral kinety 
that may have been derived from somatic kinety 1; 
it is an inverted kinety based on the inverted orien-
tation of its fibrillar associates; found in the Class 
 KARYORELICTEA (e.g., Loxodes ). 
Pseudolorica : an enclosure derived by allometric 
growth of the external sheath of the stalk, caused 
by very rapid secretion of outer stalk material; 
found in peritrichs , such as Opercularia . 
Pseudomembranelle : rather imprecise term used 
variously in the literature to describe oral or 
somatic ciliary complexes that seem to defy classi-
fication, but do appear to resemble some kind of 
membranelle sensu lato or complex kinetofrag-
ment ; see Frange and Pavés . 
Pseudonasse : see Rhabdos . 
Pseudoperistome : term formerly used for the vesti-
bulum of trichostomes and colpodeans . 
Pulsating Canal : see Afferent Canal . 
Pulsating Vacuole : see Contractile Vacuole . 
 Q 
Quadrulus (pl. Quadruli ): buccal polykinetid
with long cilia and an infraciliary base, typically 
four kinetosomes in width and many in length; the 
lengthy rows are more loosely associated than is 
the case in peniculi and membranelles sensu stricto
(e.g., in Paramecium ); synonyms include mem-
brana quadripartita, Vierermembran, and vierteilige
Membran.
 R 
Radial Canal : see Afferent Canal . 
Radial Fibers : see Postciliary Microtubules . 
Glossary 49
Radial Pins : see mention under Border Membrane . 
Reactive Budding : budding in response to stress-
ful environmental conditions. 
Recapitulation, Law of : see Biogenetic Law . 
Receiving Vacuole : see Cytopharyngeal Pouch . 
Regeneration : a process in which parts of the 
body are developed anew after loss by either natu-
ral accidents or experimental manipulations. See 
Morphogenesis . 
Reorganization Band : see Replication Band . 
Replication Band : lightly staining, though with a 
narrow Fuelgen-positive leading edge, cross-band 
of a macronucleus that migrates or sweeps along 
the length of the nucleus of spirotrichs ; in short 
macronuclei, one band and in longer macronuclei 
(e.g., in some hypotrichs) with a similar band 
traversing the other half either from midpoint 
out to the ends or from ends into the center; the 
replication band is involved in DNA replication 
and histone synthesis, the amounts of these sub-
stances doubling just behind the moving bands; 
in the homomerous macronuclei of spirotrichs , 
preceding macronuclear fission and cytokinesis of 
the organism itself; two zones may be recognized 
– the reticular (“forward zone” or “solution plane,” 
as formerly known) and the diffuse (“rear zone” 
or “reconstruction plane”, which is the locus of 
the DNA synthesis); an analogous (?) structure 
may also occur in the heteromerous macronucleus
of certain phyllopharyngeans where there is only 
one band, moving across the orthomere (RB, Fig. 
2.12s, 2.12t, 2.12x). 
Reproduction : note that, though there are a number 
of types of fission , the only kind of reproduction in 
ciliated protozoa is asexual , textbook statements 
notwithstanding (i.e., conjugation , for example, is 
a sexual phenomenon but not sexual reproduction); 
see Fission . 
Reticulated Fiber : see Filamentous Reticulum . 
Retractor Fibers : generalized term for bundles of 
myonemes , used to draw back some extended part 
of the body or a protruding oral region (RF, Fig. 
2.5Af).
Retrodesma (pl. Retrodesmata ): see Retrodesmal 
Fiber . 
Retrodesmal Fiber : rarely occurring non-striated 
fiber arising close to the base of a somatic kineto-
some near its microtubular Triplets Numbers 5–7 
and, unlike the kinetodesma , extending posteriad 
and parallel to the pellicle (e.g., in certain cleve-
landellid armophoreans ); may be a homologue by 
positional similiarity of the kinetodesma; could be 
called a retrodesma (pl. retrodesmata) (Rd, Fig. 
2.1Ec, 2.1Ed). 
Rhabdocyst : rod-like extrusome composed of a 
shaft topped by a conical cap; on extrusion, the cap 
and distal part of the shaft remain unchanged, but 
are anchored(?) in the cell by a bulbous expansion 
of the basal portion of the organelle; found in cer-
tain karyorelicteans (Fig. 2.9Ca). 
Rhabdos : the tubular cytopharyngeal apparatus
whose walls are strengthened on the outside by 
bundles of nematodesmata and often lined longi-
tudinally both by transverse microtubules derived 
from circumoral kinetosomes and by bulge micro-
tubules whose origin is undetermined; contains 
specialized phagoplasm , sometimes with included 
toxicysts ; may be bound, near its proximal (outer) 
end, by an expansible filamentous annulus ; show-
ing a range of complexity in its own composition 
from a loose organization in some vestibulifer-
ans , which lack toxicysts, to the more elaborate 
structure in prorodontids and haptorians ; principal 
synonyms of rhabdos include pseudonasse, and 
the recently used clathrum; clathrum is here con-
sidered totally inappropriate in view of its clear 
implication of a lattice work, whereas the rhabdos 
is actually both overall, and in its principal separate 
parts, highly reminiscent of a rod or rods, thus its 
name, arranged in a straight, non-curved, encir-
cling palisade formation, with perhaps a suggestion 
of fluting; see Cyrtos (Fig. 2.7j). 
Ribbed Wall : non-ciliated lining or surface of the 
right side of the buccal cavity of many oligohy-
menophoreans , ultrastructurally, appearing ribbed 
due to the presence there of microtubular ribbons , 
presumed to be postciliary microtubules that arise 
in association with the kinetosomes of the nearby 
paroral ; considered to be naked, typically when 
no pellicular alveoli are involved posterior to the 
cytostome , thus in the cytopharynx ; considered 
to be non-naked when oral ribs are present; the 
ribbed wall on the right side is sometimes called the 
50 2. Glossary of Terms and Concepts Useful in Ciliate Systematics
primary ribbed wall, while the much rarer second-
ary ribbed wall is said to occur on the left side of 
the buccal cavity. 
Rod, Cytopharyngeal : see Nematodesma . 
Rod, Pharyngeal : see Nematodesma . 
Rootlet : any fibrillar or microtubular structure 
originating from or near a kinetosome and extend-
ing into the cytoplasm away from the pellicle ; see 
Nematodesma . 
Rosette : unique septate structure near the cyto-
stome of many apostomes ; also used to describe 
the result of several rapid preconjugation divisions 
of certain peritrich zooids in production of free-
swimming microconjugants

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