OF THE VORTICELLINA. 



585 



This species is liable to be mistaken, by 

 an inexperienced observer, for a free Vo?-- 

 ticella ; its true distingnisliing character 

 appears to be its open wreath of cilia. 

 1-1500" to 1-860". 



T. Mitm (Siebold) (xxix. 16).— An- 

 terior segment elongated, cylindrical, 

 much longer than the slightly wider and 

 more discoid posterior segment, into 

 which it gradually expands. The outer- 

 most margin of the posterior segment 

 has a similar wreath of cilia to that of 

 T. Pedicidus ; but the prehensile appa- 

 ratus difiers in the two species. In T. I 



Mitra the undulating cartilaginous ring 

 is not armed with hooks, but has only 

 the annular membrane, precisely like 

 that in the other species, except that 

 it is relatively smaller, less distinctly 

 striped, more colourless and transparent, 

 and therefore more readily overlooked. 

 Between the two segments is the deep 

 fmit)w in which the mouth is placed, 

 from which a row of cilia extends to- 

 wards each end at right angles to the 

 posterior ciliary zone, and is homologous 

 with the anterior wTeath of cilia of T. 

 Pedicidus. 



Genus UEOCEjS'TEFM (X. 231, 232).— Free, with a tail-like style, but 

 no pedicle, and no cilia, except a wreath anteriorly ; oral aperture simple. 

 Self-division transverse. Ehrenberg thinks the eyes, which MiiUer supposed 

 he had seen, were most probably the traces of cilia, which he appears to have 

 overlooked. 



Ubo CENTBUM jTi^rSo {Cercciria Turho, j ticella-^toW, but an articulated style on 

 M.) (x. 231, 232). — Hyaline, ovate, tri- j the back — perhaps a foot." WithLemnae 

 lateral, with a style, or setaceous tail, I and Confervpe. Fig. 232 a dorsal, 231 a 

 one-third of its length. Ehrenberg says, { side view. 1-430" to 1-280". 

 " The little tail is not a separable Voy- \ 



Genus A^OETICELLA (XXYII. 1-5).— Crowned with cilia anteriorly; 

 stalked when young, but at a later period, and also after self-division, sessile. 

 The shape of the zooids, when stalked, is similar ; the pedicle can be suddenly 

 deflected spirally, by means of the long muscle within it, but it is never 

 branched. At certain periods a second wreath of cilia is produced at the 

 posterior part of the body. Xot only, according to Ehrenberg, can numerous 

 stomach- cells be seen, but likewise the gradual passage of the food onwards, 

 in a twining sort of intestinal canal, though this is not easily observed, on 

 account of the periodical deflection of the pedicle. However, in the genera 

 Epistylis and Opercidaria, whose pedicles are comparatively motionless, the 

 nutritive apparatus may be much more perfectly investigated. The mouth 

 and discharging orifice are separate, but he in the same hollow, at the anterior 

 margin. The granules are variously coloured, and constitute, in Ehrenberg's 

 language, clusters of ova ; nucleus elongated, contractile bladder round. The 

 animalcules are androgynous. The supposed increase by the growth of young 

 animalcules out of the pedicle (or of gemmae), Hke flowers on the stem of a 

 plant, has arisen from erroneous observation. When the animalcule loosens 

 itself from its pedicle or stalk — a circumstance which, says Ehrenberg, '' takes 

 place at certain periods — the stalks die, or disappear, just like the shells of 

 crabs, or as the nails and hair." The muscular fibre within the stem requii'es 

 stops, or an achromatic condenser, under the stage, to render it distinct. 



The VorticeUce being of so considerable a size, and easily procurable, have 

 formed the subject of numerous investigations into their organization ; but 

 yet no observers have been able to coincide entirely with the views of 

 Ehrenberg. Among the most recent researches are those of Prof. Stein, 

 which have been fuUy put forward in the general history of these animals, 

 to which we must refer (see p. 277 et seq.). Suffice it to say that the 

 winding intestinal canal, the distinct stomach- cells, the clusters of ova, the 

 androgynous nature mentioned in the above account from Ehrenberg of the 

 internal organization of VorticeUce, have, not only in Stein's opinion, but in 



