830 THE ANIMAL KINGDOM. 



Paranuclei, Maupas, A. Z. Expt. ix. 1881, p. 360. Gas bubble in a Sphae- 

 rophrya, Engelmann, Z. A. i. 1878, p. 152. 



Fission : Urnula, Clapar^de and Lachmann, Eludes sur les Infusoires, etc. ii. 



1860-1, p. 208; Podophrya libera-=fixa, Maupas, A. Z. Expt. v. 1876, p. 409; P. 



fixa, Cienkowski, Bull. Imp. Acad. St. Petersburgh, xiii. 1855, columns 299-300; 



Carter, A. N. H. (3), xv. 1865, p. 287; P. mollis, note 2, p. 827, ante; Acineta 



mystacina, Biitschli, J. Z. x. 1877, p. 307 ; cf. Gruber, Z. W. Z. xxxvi. 1882, p. 118. 



Gemmation, (i) External; Hemiophrya= Podophrya gemmipara, R. Hertwig, 

 M. J. i. 1876 ; H. = P. Benedeni, Fraipont, op. cit. supra, xlv. p. 278 ; Ophryoden- 

 dron Belgicum, Id. op. cit. xliv. p. 784. (2) Internal; Podophrya quadripartita, 

 Biitschli, J. Z. x. 1877 ; Trichophrya, Id. ibid. p. 308; Dendrocometes, Plate, op. cit. 

 supra. Cf. note i, p. 828, ante. Embryoes are described in the general works, 

 supra. 



Conjugation: Claparede and Lachmann, op. cit. supra, ii. pp. 122, 123, 136, 

 228-9; Fraipont, op. cit. xlv. p. 502; cf. note 2, p. 827, ante; in Dendrocometes , 

 Plate, op. cit. supra; A. Schneider, Tablettes Zoologiques, Poitiers, i. 1886, p. 82. 



CLASS INFUSORIA s. CILIATA. 



Plegepod Protozoa with a stable outline and a complete or 'partial 

 investment of cilia. Compound cilia, pectinellae, and vibratile membranes 

 are not uncommon. There is usually a special adoral band of cilia. The 

 protoplasm may or may not be differentiated into an exo- and endo-plasm, 

 and it may or may not be protected by cuticular structures. There is as 

 a rule an oral tube or cytostome, and an anal spot or cytopyge constant in 

 position, rarely an anal tube. The nucletts is single or multiple, and is 

 accompanied by one or more paranuclei, except in a few multimicleate forms. 

 A contractile vacuole is seldom absent, usually single, occasionally multiple, 

 always constant in position. Conjugation is temporary or permanent: the 

 conjugating individuals similar or dissimilar. Fission is in most instances 

 binary, sometimes repeated rapidly, causing a diminution in the size of the 

 organism. Gemmation is not common. 



The majority of Infusoria are free-swimming : a few lead a sedentary 

 but free life within a gelatinous tube, which may be simple (Stichotricha], 

 or dichotomously branched (Maryna, Schizosiphon}. Some species of 

 Stentor are able to attach themselves at will by pseudopodial processes ; 

 others inhabit a gelatinous tube, to which they cling by means of re- 

 tractile setae : so too Tintinniditim fluviatile and Stylocola. Some genera, 

 such as Spirochona and its allies, are permanently attached by a sucker- 

 like disc or by a cement. Of the attached forms, some are simple, and 

 then naked, stalked, e. g. Vorticella, or tubicolous, the tube or lorica 

 being sessile or stalked ; others are colonial, either naked and stalked, 

 e. g. Epistylis, or protected by a gelatinous investment as in Ophrydium. 



