Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/887

Rh CILIATA,] PROTOZOA 863 Diagrammatic optical section of a Ciliate Protozoon, showing all structures except the contractile vacuoles. a, nucleus; b, paranucleus (so-called nucleolus) ; c, cortical substance ; D, extremely delicate cuticle ; E, medullary (more fluid) protoplasm ; f, cilia; &amp;lt;/, trichocysts ; h, filaments ejected from the trichocysts ; i, oral aperture ; k, drop of water contain ing food-particles, about to sink into the medullary substance and form a food-vacuole ; I, m, n, o, food-vacuoles, the successive order of their formation corresponding to the alphabetical sequence of the letters ; the arrows indicate the direction of the movement of rotation of the medul lary protoplasm ; p, pharynx. 3. Outline of a Ciliate (Paramoecium), to show the form and position of the contractile vacuoles. 4-7. Successive stages in the periodic formation of the contractile vacuoles. The ray-like vacuoles discharge their contents into the central vacuole, which then itself bursts to the exterior. 8-15. Diagrams of the changes undergone by the nucleus and paranucleus of a typical Ciliate during and immediately after conjugation: N, nucleus; pn, paranucleus; 8, condition before conjugation ; 9, conjugation effected ; both nucleus and paranucleus in each animal elongate and become fibrillated ; 10, two spherical paranuclei pn 2 in each, two dividing or divided nuclei 2S&quot; 4 ; 11, the spherical paranuclei have become fusiform ; 12, there are now four paranuclei in each (pn* and pn x ), and a nucleus broken into four or even more fragments ; 13, the two paranuclei marked pn* in 12 have united in each animal to form the new nucleus pn* ; the nuclear fragments are still numerous ; 14, after cessation of conjugation the nuclear fragments N and the two unfused paranuclear pieces pn* are still present ; 15, from a part or all of the fragments the new paranucleus is in process of formation, the new nucleus (pn* = N) is large and elongated. 16. Diagram of a Oiliate in process of trans verse fission. 17. Condition of the nucleus N, and of the paranucleus pn in Paramoecium aurelia after cessation of conjugation as observed by Biitsohli. 18. Stylonichia mytilus (one of the Hypotricha), showing endoparasitic unicellular organisms b, formerly mistaken for spores ; a, nuclei (after conjugation and breaking up). Fain. 7. OPHRYOSCOLEOID.&amp;gt;E. Genera. Astylozoon, Engelm. ; Ophryoscolex, Stein. Sub-order 2. SKDENTARIA, animals always attached or sedentary during the chief part of the life-history. Fain. 1. VORTIOELUD.E. Animals ovate, campanulate, or sub- cylindrical ; oral aperture terminal, eccentric, associated with a spiral fringe of adoral cilia, the right limb of which descends into the oral aperture, the left limb encircling a more or less elevated protrusible and retractile ciliary disk. Sub-family 1. Vorticellinse : animalcules naked. a. Solitary forms. Genera. Gerda, Cl. andL. ; Scyphidia, Dujnrd. ; Spirochona, Stein (sessile with peristome in the form of a spirally convolute mem branous expansion, Fig. XXIII. 10) ; Pyxidium, Kent (with a non-retractile stalk) ; Vorticella, Linn, (with a hollow stalk in which is a contractile muscular filament). /3. Forming dendriform colonies. Genera. Carchesium, Ehr. (Fig. XXIII. 18, with contractile stalks) ; Zoothammium, Ehr. (contractile stalks) ; Epist.ylis, Ehr. (stalk rigid) ; Opercularia, Stein (stalk rigid, ciliated disk oblique ; an elongated peristomial collar, Fig. XXI II. 20). Sub-family 2. Vaginieolinae : animalcules secreting firm cup-like or tube-like membranous shells. Genera. Vaginicola, Lamarck (no internal valve); Thuricola, Kent (with a door-like valve to the tube, Fig. XXIII. 25, 26) ; Cothurina, Ehr (lorica or shell pediculate ; no operculum) ; Fyxicola, Kent (lorica pedunculate, animal carrying dorsally a horny oper culum, Fig. XXIII. 21, 22). Sub-family 3. Ophrydina : animalcules secreting a soft gelatinous envelope. Genera. Ophionella, Kent; Ophrydium, Ehr. OKDER 2. HETEROTRICHA, Stein. Characters. A band or spiral or circlet of long cilia is developed in relation to the mouth (the heterotriehous band) corresponding to the adoral circlet of Peritricha ; the rest of the body is uniformly beset with short cilia. a. Heterotrichal band circular. Genera (selected). Tintinnus, Schranck (Fig. XXIII. 3); Tri- chodinopsis, Cl. and L. ; CodnneUa, Haeck. (with a peri-oral fringe of lappet-like processes) ; Calceolus, Diesing. . Heterotrichal band spiral. Genera (selected). Stentor, Oken (Fig. XXIII. 2) ; Elepharisma, Perty (with an undulating membrane along the oral groove); Spirostomum, Ehr. (oral groove linear and elongate, Fig. XXIII. 1); Leucoplirys, Ehr. (oral groove very short). 7. Heterotrichal band in the form of a simple straight or oblique adoral fringe of long cilia. Genera (selected). Bursaria, Miiller ; KycMhe.rus, Leidy (with well-developed alimentary tract and anus, Fig. XXIV. 22) ; Balan- tidium, Cl. and L. (B. coll parasitic in the human intestine). OIIDER 3. HOLOTRICHA, Stein. Characters. There is no special adoral fringe of larger cilia, nor a l&amp;gt;and-like arrangement of cilia upon any part of the body ; short cilia of nearly equal size are uniformly disposed all over the surface. The adoral cilia sometimes a little longer than the rest. a. With no membraniform expansion of the body wall. Genera. Paramoecium, Ehr. (Fig. XXV. 1, 2) ; Prorodon, Ehr. (Fig. XXIV. 13); Coleps, Ehr. ; Enchelys, Ehr. ; Trachelocerca, Ehr. ; Trachelius, Ehr.; Amphileptus, Ehr.; Icthyophthirius, Fouquet (Fig. XXIV. 15). /3. Body with a projecting membrane, often vibratile. Genera. OphryogUna, Ehr.; Colpidium, Stein; Lcmbus, Cohn ; Trichonympha. Lcidy (an exceptionally modified form, parasitic, Fig. XXIV. 3). 7. Isolated parasitic forms, devoid of a mouth. Genera. Opalina, Purkinje (nuclei numerous, no contractile vacuole, Fig. XXIV. 4 to 8) ; Bencdcnia, Foett. ; Opalinopsis, Foett. (Fig. XXIV. 1, 2); Anoploplirya. Stein (large axial nucleus, numerous contractile vacuoles in two linear series, Fig. XXIV. 9 10) ; Haptophrya, Stein ; Hoplitoplirya, Stein. ORDER 4. HYPOTRICHA, Stein. Characters. Ciliata in which the body is flattened and the locomotive cilia are confined to the ventral surface, and are often modified and enlarged to the condition of muscular appendages (setae so-called). Usually an adoral band of cilia, like that of Heterotricha. Dorsal surface smooth or provided with tactile hairs only. Mouth and anus conspicuously developed. a. Cilia of the ventral surface uniform, fine, and vibratile. Genera. Chilodon, Ehr. ; Loxodes, Ehr. ; Dysteria, Huxl. ; Hiixleya, Cl. and L. /8. Cilia of the ventral surface variously modified as sette (muscular appendages), styles, or uncini. Genera. Stylonichia, Ehr. (Fig. XXV. 18); Oxytricha, Ehr.; Euplotes, Ehr. (Fig. XXIV. 20, 21). Further remarks on the Ciliata. The Ciliata have recently formed the subject of an exhaustive treatise by Mr Saville Kent (71) which is accessible to English readers. On the other hand Prof. Biitschli has not yet dealt with them in his admirable critical treatise on the Protozoa. Hence a large space has not been devoted in this article to the systematic classification, and enumeration of their genera. See (79) and (93). One of the most interesting features presented by the group is the presence in many of a cell anus as well as a cell mouth (Fig. XXIV. 22, d). In those devoid of an anus the undigested remnants of food are expelled either by a temporary aperture on the body-surface or by one opening into the base of the pharynx. In many parasitic Ciliata, as in higher animal parasites, such as the Cestoid worms, a mouth is dispensed with, nutriment being taken by general imbibition and not in the solid form. Many Ciliata develop chlorophyll corpuscles of definite biconcave shape, and presumably have so far a capacity for vegetal nutrition. In Vorticella viridis the chlorophyll is uniformly diffused in the pro toplasm and is not in the form of corpuscles (72). The formation of tubes or shells and in connexion therewith of colonies is common among the Peritricha and Heterotricha. The cuticle may give rise to structures of some solidity in the form of hooks or tooth-like processes, or as a lining to the pharvnx (Fig. XXIV. 12). The phenomena connected with conjugation and reproduction are very remarkable, and have given rise to nmnt-rons misconcep tions. They are not yet sufficiently understood. It cannot be surely asserted that any Ciliate is at the present time known to break up, after encystment or otherwise, into a number of spores, although this was at one time supposed to be the rule. Icthyoph- thirius (Fig. XXIV. 15 to 18) and some Vorticella? (76) have been stated, even recently, to present this phenomenon ; but it is not impossible that the observations are defective. The only approach to a rapid breaking up into spores is the multiple formation (eight) of microgonidia or microzooids in Vorticellidse (Fig. XXIII. 11, 12); otherwise the result of the most recent observations appears to- be that the Ciliata multiply only by binary fission, which is very frequent among them (longitudinal in the Peritricha, transverse to the long axis in the others). Several cases of supposed formation of spores within an adult Ciliate and of the production endogeuously of numerous &quot;acineti- form young &quot; have been shown to be cases of parasitism, minute unicellular parasites, e.g., parasitic Acinetse (such as Sphserophrya described and figured in Fig. XXVI.) being mistaken for the young. The phenomenon of conjugation is frequent in the Ciliata, and is either temporary, followed by a separation of the fused individuals, as in most cases, or permanent, as in the case of the fertilization of normal individuals by the microgonidia of Vorticellid*. Since the process of conjugation or copulation is not followed by a formation of spores, it is supposed to have merely a fertilizing effect on the temporarily conjoined individuals, which nourish themselves and multiply by binary fission more actively after the process than before (hence termed &quot;rejuvenescence).&quot; Remarkable changes have been from time to time observed in the nuclei of Ciliata during or subsequently to conjugation, and these were erroneously interpreted by Balbiani (73) as indicating the formation of spermatozoa and ova. The nuclei exhibit at one period great elongation and a distinct fibrillation, as in the dividing