ACINETARIA. 829 



-may attain a height of T \y in. ; and the zooids of Ophryodendron abie- 

 tinum a length of ^ in. 



The affinities of the Acinetaria are very obscure. The fact that the bud is 

 ciliated does not necessarily attach them to Infusoria, and Stein's view that they are 

 embryonic forms of different Infusorians has been laid to rest long ago. It is 

 probable, however, that they are descended from ciliated ancestors, and a re- 

 markable Infusorian, Actinobolus radians, is known which is provided with retractile 

 tentacles. The latter appear to be used for the softening of the cellulose mem- 

 brane of the cells of Cladophora; see Ge"za Entz, Z. W. Z. xxxviii. pp. 169, 171-2. 

 He points out that the ends of the tentacles in Acinetaria kill and assist in breaking 

 up the prey. See his remarks on affinities, pp. 173-5. 



The Acinetaria are classified as follows by Saville Kent : 



I. Suctoria. Suctorial tentacles, with or without adhesive tentacles (= 

 retinacula). 



(a) Non-colonial. Rhynchaetidae, one or two tentacles only : Rhynchaeta, 

 motile and naked ; Urnula, sessile and loricate. Acinetidae, tentacles simple and 

 numerous ; (i) naked, with tentacles all suctorial, the free-swimming Sphaerophrya, 

 the sessile and irregularly shaped Trichophrya, the pedicellate Podophrya, or with 

 tentacles suctorial and adhesive, Hemiophrya ; (2) loricate with suctorial tentacles, 

 the sessile Solenophrya, the pedicellate Acineta, with tentacles suctorial and 

 adhesive, Podocyathus. Dendrocometidae, sessile, with 4-6 branched arms, Den- 

 drocometes paradoxus. 



(b) Colonial. Dendrosomidae, sessile, with branched stems and stolon, Den- 

 drosoma radians. 



II. Actinaria (s. Non-Suctoria, E. Ray Lankester). Only retinacula. 

 Ephelotidae, tentacles simple, ray-like; animals pedicellate; the naked Ephelota, 



and loricate Actinocyathus. Ophryodendridae, tentacles represented by one or more 

 retractile proboscidiform organs; the organ simple, Acinetopsis, or with terminal 

 cirri, Ophryodendron; but see note i, p. 827, ante. 



Plate proposes (Z. W. Z. xliii. p. 198) to divide the class into (i) Radiformiae, 

 with isolated tentacles, and (2) Fascicularia, with tentacles borne upon arms or 

 proboscides. The second subdivision includes Dendrocometes and Ophryodendron. 



Saville Kent, Tentaculifera, Manual of the Infusoria, ii. 1880-1, pp. 801-56; 

 Maupas, 'Contributions,' etc. A. Z. Expt. ix. 1881 ; Fraipont, ' Recherches/ etc. 

 Bull. Acad. Roy. Belg. xliv. 1877; xlv. 1878; R. Hertwig, ' Beitrage,' etc. M. J. 

 i. 1876, pp. 50-80. 



Rhynchaeta, Zenker, A. M. A. ii. 1866, p. 345. Acineta gelatinosa, Buck, Ber. 

 Senck. Ges. 1884; Adnetae and Ophryodendron variabile, Gruber, Nova Acta, xlvi. 

 1884, pp. 526-33; Dendrocometes, Plate, Z. W. Z. xiii. 1886, pp. 175-200. Many 

 Acinetaria are described in papers relating to Infusoria : such papers are denoted 

 by an asterisk on p. 839, infra. 



Changeability of form : in Acineta Livadina, Mereschkowski, A. N. H. (5), vii. 

 1 88 1, p. 214; in Ophryodendron variabile, Gruber, op. cit. supra. 



Assumption of a motile phase. Podophrya libera = P. fixa var. Algirensis, 

 Maupas, A. Z. Expt. v. 1876; P. fixa, R. Hertwig, op. cit. p. 78, note; Acineta 

 mystacina, Biitschli, M. J. x. 1877, p. 307 ; Dendrocometes, Plate, op. cit. supra. 



