CIBOTIUM. 



[ 175 ] 



CILIA. 



anotlier form, distinguished by Priiigslieira 

 under the name of Pi/f/iium, the cells are 

 globular and occur in the infested cells, 

 pushing a long tubular neck out through 

 the ceil-wtdl. In both forms the contents 

 of the C/iri/(ridhan-ce\l are tinally resolved 

 into ciliated gonidia, which escape and 

 swim about. lu the external form, the cell 

 often opens by a lid (like the androspore 

 cells of G^DOGONiuJi); in the internal form 

 the slender neck opens at the end. Braun 

 has described no less than twenty -three of 

 these obscure bodies, while Eabenhorst 

 admits six species ; and they have been 

 observed by Cohn, who connects them with 

 Achh/a, considering them aquatic fimgi. 

 Carter has observed them in Spirof/t/ra ; and 

 we have found both forms in and on the 

 cells of Chlorosph.t'.ra. Braun and Cohn 

 declare them to be really foreign bodies, 

 that is, true parasites; but we are not clear 

 on this point ; they seem rather products 

 of diseased protoplasm, if they be not modi- 

 fications of the antheridial structures of 

 some of the Confervoids. 



BiBi.. Al. Braun, Verjiinqunfj ^-c. (liai/ 

 Trand. 1853, 185); Berl. Abhdndl. 1856,2 

 (plates) ; Ueb. CJuitridhim, Berlin, 1856 ; 

 Alff. Unicell. Gen. A"or. Leipsic, 1855 ; Bail, 

 Bot. Zeit. xiii. 678 ; Cienkowski, Bot. Zeit. 

 XV. 233 ; Carter, Attn. Nat. Hist. 2nd ser. 

 xvii. 101, and xix. 259 ; Barv & Woronin, 

 Ber. Geselkch. Freih. 18ti3 ; AYoronin, But. 

 Zeit. 1868, 81 ; Nowakowski, Cuhn, Biol, d, 

 Pfl.\. 1, ii.l877, 73, 201. 



CIBOTIUM, Kaulfuss. — A genus of 

 Dicksoniese (Polypodiaceous Ferns) ; with 

 a bivalve indusium ; now made a subgenus 

 of Dicksonia. 



BiBL. Hooker, 81/71. Fil. 49. 



Fig. 127. 



Cibotinm macrocari.um. 

 A pinnule with sori. Magnified 10 diameters. 



CILIA (plural of ciliuvi) of Animals. — 

 These are microscopic filaments attached by 

 one end to the surfaces of various parts of 

 animals, and exhibiting a vibratory or rota- 

 tory motion. They are usuall}^ rounded and 



broadest at the base, tapering towards the 

 free end ; sometimes they are flattened. 

 Their length is very variable, having been 

 estimated at 1-50,000 to 1-500" ; probably 

 1-15,000 to 1-500" would include most of 

 them ; in Bacterium termo they are 

 1-200,000" in diameter (Dallinger). The 

 larger size is attained by the cilia existing 

 on the point or angle of the giUs or branchial 

 laminse of the whelk {Buccinmn undatum). 



Numerous examples of animals furnished 

 with cilia, showing their appearance when 

 at rest, are figured in Pis. 30, 31, 32, 43, & 

 44. During life, and for some time after 

 death, they are usually in constant motion, 

 giving the parts of the field of the micro- 

 scope in which they are situated a tremulous 

 appearance when their motion is very rapid 

 and the cilia are very minute. When they 

 are large, as on the gills of the common 

 sea-mussel (IMytilus), especially when 

 their motion is slackening, they are seen 

 waving to and fro, or lashing the water, and 

 producing in it strong currents, rendered 

 visible by the motion of minute particles 

 accidentally contained in the water. The 

 motion is mostly uniform, or in one direc- 

 tion ; occasionally, however, it has been 

 observed to cease for a moment, and then 

 to assume an opposite direction to that pre- 

 viously exhibited. During the motion, the 

 whole filament is usually more or less 

 cuned ; but in some instances among the 

 Infusoria, the basal portion of the cilia re- 

 mains rigid, whilst the terminal portion 

 vibrates ; under these circumstances the 

 cilia are distinguished as flagellifi>nu fila- 

 ments. Sometimes the cilia move around 

 an imaginary perpendicular axis, in a rota- 

 ting direction. 



Cilia are found in all the Vertebrata, and 

 in the Invertebrata, excluding the Crustacea, 

 Arachnida, and Insecta. We have, on two 

 occasions, distinctly obtained cihated epithe- 

 lium, resembling that in PL 49. fig. 13, by 

 womidingthe bodies of the larva3 of garden- 

 moths ; but were unable to follow the obser- 

 vations. In Man; they spring from epithelial 

 cells ; the localities in which they are foimd 

 are stated under Epititeliltsi. 



The uses of the cilia are of two kinds : 

 when the body to which they are attached 

 is of no great bulk or specific gi-avity com- 

 pared with that of the medium in which 

 they reside, the cilia become organs of loco- 

 motion, as in the Kotatoria, Infusoria, the 

 young AcalephjE, the ovum, &c. ; but if 

 the inertia of the body be too great to be 



