CIBOTIUM. 



[ 175 ] 



CILIA. 



another form, distinguished by Pringsheim 

 under the name of Pythium, the cells are 

 glohular and occur in the infested cells, 

 pushing a long tubular neck out through 

 the cell-wall. In both forms the contents 

 of the Chrytridium-cell are finally resolved 

 into ciliated gonidia, which escape and 

 swim about. In the external form, the cell 

 often opens by a lid (like the androspore 

 cells of (EDOGONIUM); in the internal form 

 the slender neck opens at the end. Braun 

 has described no less than twenty-three of 

 these obscure bodies, while Rabenhorst 

 admits six species; and they have been 

 observed by Cohn, who connects them with 

 Achlya, considering them aquatic fungi. 

 Carter has observed them in Spirogyra ; and 

 we have found both forms in and on the 

 cells of CHLOROSPHJERA. 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. 



BIBL. Al. Braun, Verjungung 8fc. (Ray 

 Transl. 1853, 185); Berl. AbhandL 1856, 2 

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

 Alg. Unicell. Gen. Nov. Leipsic, 1855 ; Bail, 

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

 xv. 233 ; Carter, Ann. Nat. Hist. 2nd ser. 

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

 Ber. Geselhch. Freib. 1863 ; Woronin, Bot. 

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

 Pfl.i.l, ii. 1877, 73, 201. 



CIBOTIUM, Kaulfuss. A genus of 

 Dicksonieae (Polypodiaceous Ferns) ; with 

 a bivalve indusium ; now made a subgenus 

 of Dicksonia. 



BIBL. Hooker, Syn. Fil. 49. 



Fig. 127. 



Cibotium macrocarpum. 

 A pinnule with sori. Magnified 10 diameters. 



CILIA (plural of ciUum) 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 usually 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 gills or branchial 

 laminae of the whelk (Biiccinum 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 (MYTILUS), 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 

 curved; 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 flagelliform 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 ciliated epithe- 

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

 wounding the bodies of the larvae of garden- 

 moths ; but were unable to follow the obser- 

 vations. In Man, they spring from epithelial 

 cells ; the localities in whicn they are found 

 are stated under EPITHELIUM. 



The uses of the cilia are of two kinds : 

 when the body to which they are attach'ed 

 is of no great bulk or specific gravity 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 Acalephaa, the ovum, &c. ; but if 

 the inertia of the body be too great to be 



