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(End, Fig. 2.12r, 2.12bb). Endosprit : old term for the very short suctorial tentacle of the curious suctorian Cyathodinium . Endosymbiont ( of Ciliates ): symbiont , generally bacterial or algal in nature, living within the cytoplasm or nucleoplasm of a ciliate cell; rang- ing from kappa particles and other \u201cGreek-letter parasites\u201d of Paramecium , bacteria often inti- mately involved genetically and metabolically with their host, to the common zoochlorellae and zooxanthellae found widespread among ciliate groups; see Xenosome . Envelope : used variously; for example, Cortex , Lorica , and Nuclear Envelope . Epiapokinetal : apokinetal stomatogenesis in which the oral anlage develops on the cell surface; found in some spirotrichs . Epibionts : see Commensal . Epilorica (pl. Epiloricae ): additions to protolorica or paralorica of tintinnids; often appearing as supernumerary collars or annuli whose form, struc- ture, height, and number are variable; see Lorica , Paralorica , Protolorica . Epiplasm : fibrillar or filamentous pellicular layer directly underlying alveoli and/or plasma mem- brane ; see Lamina corticalis . Epistomial Disc : retractable, non-ciliated, vaulted center of the peristomial field characteristic of many sessiline peritrichs ; in some of the Operculariidae , the form of a prominent stalked operculum . Epistomial Lip : a cortical ridge that overlies oral structures, such as the paroral and its cilia (e.g. in some oligotrich spirotrichs and peritrich oligohy- menophoreans ). Ergastoplasm : a generally discarded term, formerly variously used for the so-called lifeless cell inclu- sions (i.e., stored fats, starches), for cytoplasmic components with affinity for basic dyes, and for a form of the endoplasmic reticulum . Erratic Kinetosomes : a single or a few kineto- somes ( ciliferous or non-ciliferous ) that appear to have \u201cwandered off\u201d from some larger, more sta- ble, infraciliary structure or organelle; may appear, or be revealable, only at certain stages in the life cycle of the organism, becoming involved (in effect as an anlage or as a vestige -turned- anlage ) in some morphogenetic process, such as stomatogenesis or budding (e.g., in suctorians). Esophagus : outmoded term not needed and mis- leading in description of any structure or cavity in the oral region. Eukaryotic : literally \u201chaving a true nucleus\u201d, organisms having a unit membrane -bound nucleus containing chromosomes or chromosome-derived gene sequences. Eupelagic : see Pelagic . Eutrophic : pertaining to an aquatic habitat with high primary productivity; high rate of anabolism; referring to a habitat rich in minerals and dissolved organic nutrients, but often with low oxygen content; similar to polysaprobic in some ways, but generally not used with regard to pollution; see Oligotrophic . Evaginative Budding : type of fission involving formation of a temporary brood pouch but in which the larval from is not freed within the parental form ; in emergence, the entire wall of the pouch evaginates and cytokinesis takes place on the out- side of the parental form; this is the characteristic mode of reproduction of members of an entire order of suctorians ; in contrast see Endogenous Budding (Fig. 2.11Cd). Evaginogemmy : see Budding and Evaginative Budding . Evolutionary Series : arrangement of groups of organisms in a supposed phylogenetic sequence, using some major character or constellation of Glossary 29 characters , as a basis for indicating a graded series from, for example, ancestral to more derived forms; see Orthogenetic Lines for the danger of possibly arbitrary and non-phylogenetic sequencing. Excystment : the process of leaving a cyst ; see Cystation , Encystment . Exogemmy : see Exogenous Budding . Exogenous Budding : type of single or multiple fission taking place essentially on the surface of the parental form ; larvae are pinched off singly or multiply, and if multiply, either synchronously or consecutively; the characteristic mode of reproduc- tion in certain chonotrichs and in one large group of suctorians (Fig. 2.11Cc). Explosive Radiation : rapid diversification of forms (e.g., into many different taxa at a given level) brought about evolutionarily by invasion of a vast new and quite different biotope by some \u201cstem\u201d group, with subsequent adaptation to the variety of specialized habitats and niches thus made avail- able to the (presumably unopposed) invader; the chonotrichs, largely symphorionts on certain crus- taceans, may well serve as an example of a group that has taken advantage of such a situation. Explosive Trichocyst : see Trichocyst . Expulsion Vesicle : see Contractile Vacuole . Expulsion Vesicle Pore : see Contractile Vacuole Pore . Extensor Membrane : largely disused term refer- ring to the ciliature of the anterior part of the paroral of certain ciliates when it is in an immobile state; the paroral cilia, forming a coalesced stiff membrane, aid in guiding food particles into the oral cavity; called Lachmann\u2019s bristle in peritrichs ; at least partially synonymous with another seldom used term, semi-membrane. External Budding : see Exogenous Budding . Extramacronuclear Microtubules : microtubules that assemble and elongate outside the macro- nuclear envelope and are used in its division; characteristic of the Class HETEROTRICHEA ; see Intramacronuclear Microtubules . Extrusive Organelle : see Extrusome . Extrusome : unit membrane -bound extrusible body located in the cortex and assembled by the Golgi apparatus ; a generalized term useful in referring to various types of probably non-homolo- gous structures (e.g., clathrocyst , cnidocyst , cono- cyst , crystallocyst , cyrtocyst , fibrocyst , haptocyst , lepido some , mucocyst , pexicyst , rhabdocyst , toxi- cyst , and trichocyst ); extrusion occurs under conditions of appropriate chemical or mechanical stimulation. Exuviotrophic : feeding on tissues or exuvial fluids of dead or molted hosts; particularly characteristic of one group of apostome ciliates. F Fascicle : generalized term, but used specifically with reference to a group or bundle of suctorial tentacles on the body of a suctorian , sometimes (but not necessarily) born on an actinophore . Fibers, Postciliary : see Postciliary Microtubules . Fibers, Transverse : see Transverse Microtubules . Fibrils : see Microfibrils . Fibrocyst : unique trichocyst characteristic of the microthoracine nassophoreans ; fusiform, explo- sive, and revealing a conspicuous parachute- or umbrella-like tip after discharge; also called a compound trichocyst. Fibrous Trichocyst : see Fibrocyst and Trichocyst . Filamentous Annulus (pl. Annuli ): \u201celastic,\u201d expansible binding of fine microfilaments sur- rounding and considered a part of the rhabdos near its proximal (outer) end; allows for the great expan- sion required by these carnivorous ciliates when feeding; said to be continuous with the lamina corticalis in the vicinity of the corona of various haptorians. Filamentous Reticulum : three-dimensional lat- tice of kinetosome-associated microfibrils present in the wall of the oral cavity or infundibulum of certain ciliates; often united at condensation nodes, giving a striking hexagonal pattern at the ultrastructural level (e.g., in some peritrichs ) (FR, Fig. 2.6Ac). Filaments : any fine fibrous components of the cytoskeleton ; see Attachment Organelle ; also an extracellular secreted structure used for attachment (e.g., Strobilidium ); see Microfilaments . 30 2. Glossary of Terms and Concepts Useful in Ciliate Systematics Filial Products : generalized term for (daughter) organisms resulting from any mode of ciliate fission ; includes tomites and buds , as well as the