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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 3−7, 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 “ unit membrane -
like” 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’s 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–2.10f). 
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 
“colored” 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 “cell drinking”; 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, 20–200 µm, and 2–20 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).