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in mucus- coatings, lorica -formation, and stalk -production; in many cases, these pores may be, in effect, some kind of parasomal sac , even kinetosome-less in the case of the bell of peritrichs and the scopuloid of suctori- ans; they have also been called cuticular pores. Pellicular Ridge : in a general way, any ridge or crest formed on the surface of the body by the underlying pellicle; often revealed as an argento- philic line of contact or juncture of the (membranes of the) adjacent, contiguous pellicular alveoli ; when, in the buccal cavity of various oligohymeno- phorans, the ridges are underpinned by postciliary microtubules and identified as oral ribs of a so-called non-naked ribbed wall . Pellicular Stria (pl. Striae ): ridges or markings in or on the pellicle ; particularly applied to the cir- cumferential annuli on the zooid of many sessiline peritrichs, rings that may be comprised of argento- philic pellicular pores and/or pellicular ridges (PelStr, Fig. 2.11B). Peniculus (pl. Peniculi ): kind of oral polykinetid in the form of a long band of often short, seemingly fused cilia; its infraciliary base, typically coursing along the left wall of a buccal cavity , may be as many as 11 kinetosomes in width but is usually only 3\u22127, with a tapering to still lower numbers at either end; known classically in peniculines like Paramecium , where there is one dorsal and one ventral peniculus; also used for the oral poly- kinetids in the infundibulum of peritrichs (although Glossary 45 see Polykinety ) and various other oligohymeno- phorans (P1, P2, P3, Figs. 2.6Ac, 2.7h). Perforatorium : see mention under Rostrum . Pericyst : a layer of material produced and depos- ited prior to the ectocyst layer and so lying upon it; often a more or less voluminous coat of mucus that may adhere the cyst to the substrate or may increase its bouyancy to enable dispersal. Pericytostomial Ciliature : cilia adjacent to and/or surrounding the cytosome ; see Oral Ciliature . Perilemma : additional outermost \u201c unit membrane - like\u201d covering the pellicle , especially in various spirotrichs . Perioral Ciliature: used to include any ciliature, properly somatic , even buccal, which is, in effect, around and/or adjacent to the oral region ; see Circumoral Ciliature . Periphyton Community : see Biofilm Community . Peristome : in a broad sense, a synonym of oral region , is well entrenched in the literature to mean the entire expansive oral region or peristomial field of peritrichs, heterotrichs, and various spirotrichs, in which the oral ciliature has often emerged from an oral cavity to encircle, though usually only partially, much of the anterior end or pole of the organism\u2019s body (Pst, Figs. 2.5Cg, 2.6A). Peristomial Area : see Peristome . Peristomial Cavity: see Buccal Cavity . Peristomial Ciliature : see Buccal Apparatus . Peristomial Field : in the strict sense, a part of the oral region delimited by the oral polykinetids or AZM of spirotrichs and heterotrichs ; this field may be barren (e.g. the spirotrich Licnophora ) or have kineties coursing across it (e.g. the heterotrich Stentor ). Perizonal Ciliature : somatic ciliature , usually to the right of the oral region , the rows of which appear to run transversely (see Parateny ); the often closely packed cilia are said to function in intensification of the food-carrying water currents that are being directed toward the oral region ; found particularly in armophorids and odontostomatids . Perkinetal : across or through the kineties ; the common mode of homothetogenic fission in ciliates in which the division furrow cuts across the body at essentially right angles to the somatic kineties (Fig. 2.11A). Pexicyst : type of small toxicyst-like extrusome in certain haptorians (e.g. Didinium ), which, on dis- charge, adheres to the pellicle of the prey without subsequent penetration. Phagocytic Vacuole : see Food Vacuole . Phagocytotic Vacuole : see Food Vacuole . Phagoplasm : specialized cytoplasm, rich in dis- coidal vesicles , found in or around the cytopharyn- geal apparatus . Phagosome: see Food Vacuole . Phagotrophic : a kind of heterotrophic nutrition in which particulate food is engulfed in a food vacuole . Pharyngeal Basket : see Cyrtos and Rhabdos . Pharynx : see Cytopharynx . Phialocyst : see Haptocyst . Phoront : stage in a polymorphic life cycle dur- ing which the organism is carried about on or in the integument of another organism, generally a metazoan; used in a much more restrictive sense to indicate the condition exhibited primarily by cer- tain polymorphic apostomes where it is a stage that is typically preceded by a tomite and followed by a trophont ; see Symphoriont (Phor, Fig. 2.9Aj). Phylembryogenesis : see mention under Biogenetic Law and Ontogeny . Phylla (pl. Phyllae ): microtubular ribbons arrayed in a somewhat radial fashion in the oral apparatus of phyllopharyngeans ; see Sucking Tube and Suctorial Tentacle (Fig. 2.10a\u20132.10f). Phylogeny : history of the race; lines of evolution involving groups of organisms through time and space; a continuum of ontogenies. Phytoplankton : see Plankton . Pigment Granules : see Pigmentocyst . Pigmentocyst : vesicles providing endogenous pig- mentation, of various colors, either in the cortex near the pellicle or deeper in the cytoplasm; many \u201ccolored\u201d ciliates derive their hues exogenously (e.g., from endosymbiotic zoochlorellae or from 46 2. Glossary of Terms and Concepts Useful in Ciliate Systematics pigments of ingested food materials) and not from pigmentocysts; see Blepharismin and Stentorin . Pinocytosis : literally \u201ccell drinking\u201d; formation of a small vesicle by endocytosis; see Parasomal Sac and Saprozoic . Pinocytotic Vesicle : see Pinocytosis . Pitelka Convention : see Numbering Conventions . Plankton : community of predominantly passively floating or weakly motile organisms (including vari- ous stages in their life cycles) on or near the surface of a body of water, fresh, brackish, or marine; if the plankton is largely plant-like (e.g., algae), it is called phytoplankton; if largely animal-like (e.g., eggs, larval stages of microcrustaceans), it is called zooplankton ; classification into net-, micro-, or nanoplankton is based on body size (diameter), >200 µm, 20\u2013200 µm, and 2\u201320 µm, respectively. Plasmalemma : synonym for plasma membrane ; sometimes used as a synonym of pellicle ; not to be confused with perilemma . Plasma Membrane : the unit membrane bounding the surface of the cell; see Unit Membrane . Plesiomorphic (adj.): see Plesiomorphy . Plesiomorphy : an ancestral character in a phyletic lineage; primitive, as in the ancestral condition; see Apomorph . Pleurotelokinetal : telokinetal stomatogenesis in which the oral anlage is derived by subequatorial proliferation of kinetosomes within several right lateral somatic kineties ; found in some colpodeans . Podite : the often conical-shaped projection from the ventral surface, near the posterior pole, of cer- tain dysteriid cyrtophorines ; a foot-like appendage, rigid though usually slightly rotatable; the structure through which or from which a glutinous, mucus- like filament may be extruded to attach or anchor the ciliate, usually only temporarily, to or over a desirable substratum; also know as a stylet, stylus or style; may be homologous to the basal, secretory part of the stalk of the related chonotrichs (Pod, Fig. 2.9Bf). Polar Basal Body-complex : grouping of kine- tosomes and sometimes parasomal sacs at the posterior end of the body of a number of forms, especially scuticociliates ; the kinetosome(s) may bear a long and often stiff caudal cilium (PBB, Figs. 2.3c, 2.3d, 2.4F, 2.7f, 2.7i).