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