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heavily armed with toxicysts , and \u2013 though ciliated and active \u2013 it is not capable of effecting extreme changes in its length; the non-homologous \u201cproboscis\u201d of Didinium is that organism\u2019s 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 \u201csand-loving\u201d; 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 \u2013 the reticular (\u201cforward zone\u201d or \u201csolution plane,\u201d as formerly known) and the diffuse (\u201crear zone\u201d or \u201creconstruction plane\u201d, 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\u20137 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