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, tactile cilia, thigmotactic cilia ), 52 2. Glossary of Terms and Concepts Useful in Ciliate Systematics the concrement vacuole (and Müller\u2019s vesicle ), organelle of Lieberkühn , palps , and the paralabial organ . Sessile : attached to substrate either by lorica , stalk , holdfast , peduncle , or other cell process; see Sedentary . Seta (pl. Setae ): see Bristle . Sexual Phenomenon (pl. Phenomena ): meiosis, haploid gametic nuclei , and a diploid synkaryon are involved; any reproduction that takes place occurs at the end of the process and is purely by asexual fission ; see Autogamy and Conjugation . Sheath : the outer portion of a peritrich stalk; see Annulus . Shell : preferred term is lorica . Sibling Species : one or more biological species that are difficult, if not impossible, to distinguish based on morphological critera; the syngens of the Paramecium \u201caurelia\u201d complex and the Tetrahymena \u201cpyriformis\u201d complex are groups of sibling species of ciliates. Silberliniensystem : see Argyrome . Silver-impregnation Techniques : cytological staining methods that permit deposition of sil- ver ions onto argentophilic sites where they are reduced, under UV light or appropriate chemicals, blackening the coated structures or areas affected and thus rendering them beautifully visible under subsequent light microscopic examination; the argyrome or silverline system so revealed in cili- ates has proven of immeasurable value in com- parative taxonomy and morphogenesis; the Klein \u201cdry\u201d method and the \u201cwet\u201d methods of von Gelei and especially of Chatton and Lwoff show up the argyrome sensu stricto , the more or less superficial \u201ccortical\u201d structures, such as the silverline merid- ians , the contractile vacuole pores , the cytoproct , and \u2013 most importantly \u2013 the (general sites of the) kinetosomes , both somatic (comprising the kineties proper) and oral (e.g., the infraciliary bases of the oral or buccal organelles ); other methods, especially Bodian\u2019s Protargol (activated silver albumose) technique and the Rio-Hortega method, additionally blacken many truly cortical organelles of the infraciliature sensu lato , deeper in the organism, such as the kinetodesmata , the nema- todesmata , extrusomes , microtubular ribbons , and myonemes , and even the nuclei , mitochondria , and contractile vacuoles , as well as the cilia them- selves, thus allowing distinction between ciliferous and barren kinetosomes (Figs. 2.3, 2.4). Silverline System : once popular synonyms are Silberliniensystem and neuroformative System; see Argyrome . Simple Ciliature : general term restricted to mean- ing individual ciliated monokinetids (e.g., those comprising a somatic kinety ) or single isolated ciliated monokinetids, such as most bristles , or cili- ated dikinetids ; excluded are formations or arrange- ments of cilia that are closely apposed in special groups or packets or blocks with some sort of interconnection, such as found in the case of cirri , somatic polykinetids , syncilia , some atrial and vestibular ciliature , and all oral \u201ccompound\u201d cili- ature, such as the paroral , undulating membranes, polykinetids , and membranelles sensu lato . Skeletal Plaques : term recently applied to the numerous polysaccharide granules assembled in the unique sucker of certain clevelandellid armo- phoreans . Skeletal Plates : term usually reserved for the long recognized and generally highly conspicuous sub- pellicular structures composed of polysaccharide reserves (i.e. amylopectin) within a fibrillar lattice; found in the entodiniomorphid vestibuliferans (i.e., ophryoscolecids and relatives); also used in reference to the uniquely calcified cuirass of the prorodontid Coleps (SP, Fig. 2.5Af). Skeletal Ring : see Denticulate Ring . Skeletogenous Structure : non-specific term usa- ble for any organelle or system (e.g., various micro- tubular ribbons , kinetodesmata , nematodesmata , various proteinaceous rods, and polysaccharide formations, which may lend a certain firmness or rigidity to the cortex or to all or part of the body of an organism); see Cytoskeleton . Solenocyst : dense vesicles found in the tentacles and subjacent cytoplasm of the suctorian cell body; fusing with the food vacuole membrane as it forms at the tentacle tip, they provide membrane and presumably contain lytic enzymes that aid in the preliminary digestion of the prey as it is ingested. Glossary 53 Solitary Form : an individual ciliate; used principally in reference to noncolonial forms in a contrasting sense; for example, there are colonial and solitary peritrich species, sometimes within a single family. Somatic Area : see Somatic Region . Somatic Ciliature : all-inclusive term for any cilia or compound ciliary organelles found anywhere on the body outside the oral region ; associated with it would be the bases of all such structures, the somatic infraciliature ; compare to Oral Ciliature . Somatic Infraciliature : see Somatic Ciliature . Somatic Kinety (pl. Kineties ): kinety confined to the somatic region . Somatic-meridional : now discarded term for a mode of stomatogenesis ; see Parakinetal . Somatic Region : general term for all of a ciliate\u2019s body except the oral region ; may be functionally subdivided (e.g., thigmotactic area ); its primary functions are locomotion, attachment to the sub- stratum, and maintenance of form. Somatization : evolutionary process of increas- ing the separation of \u201cgenerative\u201d from \u201csomatic\u201d functions in protozoa, demonstrated in ciliates in the development of nuclear dualism , in the compli- cations of sexual phenomena , in the manifestation of epigenetic morphogenesis , and in the general diversification and differentiation, often involving polymerization , of more complex structures and functions that approach almost a metazoan level of organization. Somatogenesis : the replication and development of all somatic components of the cell, usually occurring during the interfission period, but also at fission (e.g., contractile vacuole pores, cytoproct); see Stomatogenesis . Sorocarp : \u201cfruiting body\u201d developing atop an aerial stalk after aggregation of cells; found only in the colpodean Sorogena , in which the individual cells encyst as a sorocyst, a component of the sorocarp. Sorocyst : see Sorocarp . Sorogenesis : production of a sorocarp . Spasmin : see Spasmoneme . Spasmoneme : used to describe the membrane- bound bundle of contractile protein, predominantly spasmin, found in the stalks of various sessiline peritrichs ; arises from and maintains continuity with microfilaments in the bell or zooid proper; its former structural subdivision into thecoplasm and kinoplasm has not been confirmed by electron micro- scopy; see Myoneme (Sn, Fig. 2.9Bi, 2.9Bj). Spherical Colony : zooids dispersed throughout a rounded, usually gelatinous but firm, colonial mass, with body axes perpendicular to the colony surface; because of attachment to a flat substratum, the overall shape may more often be hemispherical; the framework of such a globular colony may be basically arboroid, as shown by some species of the peritrich Ophrydium whose zooids are intercon- nected by long and slender \u201cpenduncular fibers\u201d produced by their scopulae (Fig. 2.8Bb). Spica : a secant system on the right anterior surface of amphileptid pleurostomatids . Spindle Trichocyst : see Trichocyst . Spines : variously used, though especially for cer- tain apically located holdfast organelles (e.g., in some astomes); also applied to quite elaborately developed structures on the outside of the body of a number of chonotrichs ; see Attachment Organelle (Sp, Fig. 2.9Bc\u20132.9Be). Spongiome : see Spongioplasm . Spongioplasm : specialized secretory cytoplasm, of