anterior to the rosette during tomitogenesis in many apostomes ; this pointed, arch-shaped patch of specialized cilia facilitates attachment of the tomite to a new substra- tum, generally a crustacean integument. Oligomerization : postulated evolutionary process of reduction or diminution, but not necessarily sim- plification, in the usual numbers of some organelle (e.g., in numbers of kineties over a ciliate’s body); see Polymerization . Oligoploidy : see Polyploid . Oligosaprobic : see mention under Polysaprobic . Oligotrichous : having sparse somatic cilia ; typically of ciliates in the spirotrich Subclasses Oligotrichia and Choreotrichia , but also found in some stichotrichs (e.g., Halteria ) and haptorians (e.g., Didinium ); see Holotrichous . Oligotrophic : see Eutrophic . Omikron : Gram-negative bacterial endosymbiont in the cytoplasm of the hypotrich Euplotes ; often indispensable to their hosts’ life; see Xenosome . Omnivorous : eats everything(!); such ciliates are not at all “fussy” in their feeding habits. Ontogeny (pl. Ontogenies ; adj. Ontogenetic ): history of an individual, from egg to adult; by analogy, in the case of a ciliate, it is the growth and development from a filial product , the tomite , to the mature trophont or tomont , ready for another fission, in the full life cycle of the organism; comparative study of the patterns revealed in the morphogenesis associated with such ontogenetic development may throw light on the phylogeny of the group concerned (phylembryogenesis); see also Biogenetic Law . Operculum (pl. Opercula ): literally, lid or cover- ing flap; used variously (e.g., as the cover of the emergence pore of some cysts), but mostly for two quite different structures both in sessiline peritrichs : (1) the stalked epistomial disc present in many of the operculariids ; and (2) the organelle attached to the anterior end of the body, as a stalked “cap” at an oblique angle to the epistomial disc, which may wholly or partially cover the opening of the lorica on retraction of the organism into its case in some of the loricate vaginicolids (e.g., Pyxicola ) (Opr, Figs. 2.8A, 2.9Ad). Ophryobuccokinetal : buccokinetal stomatogen- esis in which the opisthe’s oral anlage derives from one to several ophyrokineties and the paroral ; found in some peniculians . Ophryokinety (pl. Ophyrokineties ): literally “brow” kinety ; one of three or more somatic kineties, often with dikinetids and single associ- ated parasomal sac forming a triangular group as revealed in silver-impregnated material; on the ventral surface near the anterior end of the body and located immediately to the right of the buccal cavity proper (e.g., in the peniculine Frontonia ); generally, but inappropriately called vestibular kineties, may represent a legitimate part of the buccal ciliature sensu lato in the organisms bearing them, and hence be considered perioral ciliature (OK, Fig. 2.7h). Opisthe : posterior filial product of a regular binary fission of the parental form ; the anterior ciliate resulting from such a division is the proter (Fig. 2.11Aa). Oral Anlage : see Anlage and Oral . Oral Apparatus (pl. Apparati ): the entire com- plex of structures and organelles involved in or directly related to the cytosome and functionally integrated for the acquisition and ingestion of food; multiple in suctorians and absent in astomatous ciliates (OA, Fig. 2.11Aa). Oral Area : see Oral Region . Oral Atrium (pl. Atria ): see Atrium . Oral Cavity : an indentation or depression that contains part or all of the oral apparatus ; see Buccal Cavity (OC, Fig. 2.5c). Oral Ciliature : simple or compound cilia that are directly associated with the oral apparatus ; associated with it would be the bases of all such structures, the 42 2. Glossary of Terms and Concepts Useful in Ciliate Systematics oral infraciliature (as opposed to kinds of somatic ciliature ). Oral Disc : specialized name for the apically located oral region of a ciliate when it is conspicu- ously separated from the rest of the body (e.g. in the hourglass-shaped spirotrich Licnophora ). Oral Groove : generalized term for a depression leading to a buccal cavity or a cytostome ; widely used in the past for Paramecium to indicate what was more recently termed vestibulum and now considered to be a kind of prebuccal area in that organism; see Vestibulum . Oral Infraciliature : see Oral Ciliature . Oral Polykinetid : general term for organellar complexes in the oral region that are composed of many, usually ciliferous kinetosomes; see Polykinetid (OPk, Figs. 2.5Aa, 2.5Ab, 2.7a, 2.7b, 2.7i; 2.4G, 2.4R, 2.7k, 2.7l). Oral Primordium : synonym of oral anlage . Oral Region : that part of the ciliate’s body bearing the oral apparatus ; convenient to use in a non-specific way; to be contrasted with the somatic region (the rest or bulk of the body); buccal area , a more restric- tive term, is not to be considered a synonym. Oral Replacement : see Stomatogenesis . Oral Ribs : argentophilic pellicular ridges of a non-naked ribbed wall ; appearing, under light microscopy, to represent lines coursing inwardly in a one-to-one ratio from the kinetosomal bases of the right-hand paroral ; found in many oligohy- menophoreans (OR, Fig. 2.7e). Organellar Complex : consistently recognizable subcellular structures responsible for subsidiary cell functions and composed of a specific associa- tion of unit organelles ; see Organellar System . Organellar System : an organization of organel- lar complexes integrated to perform a major (i.e., systemic) cellular function (e.g., locomotion, osmoregulation, feeding and ingestion, digestion). Organelle of Fixation : see Attachment Organelle . Organic Pollution : see Polysaprobic and Saprobity System . Orthogenetic Line : supposed evolutionary series that has allegedly followed a predetermined pathway and has not invoked nor been subject to the laws of natural selection; such proposed phylogenetic lines are rejected by modern evolutionary theory. Orthography : correct or conventional spelling. Orthomere : DNA-rich karyomere of a heteromer- ous macronucleus ; to be contrasted with the para- mere , the other kind of karyomere in that type of nucleus (Om, Fig. 2.12r, 2.12bb). Orthonematocyst : extrusome in which the mate- rial to be extruded appears as a capped, straight tubular filament embedded in a matrix whose outer portion appears to be composed of myelin-like sheets; the ciliate organelle is unlikely homologous to the nematocyst of the cnidarians; found in the karyorelictean Remanella . Osmotrophic : see Saprozoic P Palintomic (adj.): see Palintomy . Palintomy (adj. Palintomic ): rapid sequence of binary fissions , typically within a cyst and essentially without intervening growth, resulting in production of numerous, small-sized filial products or tomites ; characteristic of various parasitic ciliates, including some apostomes, the hymenostome Ichthyophthirius , and a few others; the net result is similar to that of polytomic divison (Fig. 2.9Af, 2.9Ah). Palp : variously used, often for a protuberance of the body with an alleged sensory function. Papilla (pl. Papillae ): variously used; often referring to the pellicular or extrapellicular wart-like bumps or small protuberances on the surface of an organism (e.g., on the bell of some sessiline peritrichs and on the body of certain chonotrichs ); in a broad sense, tubercle may be considered a synonym. Paradiploid : condition of ploidy of the macronu- cleus of karyorelicteans ; very close to the diploid DNA amount, hence “para”-diploid; see Diploid and Polyploid . Parakinetal : type of stomatogenesis in which the anarchic field of kinetosomes