oSi 



SYSTEMATIC HISTORY OF THE INFUSOEIA. 



incompletely observed beings. Thus T. Gnindinella and T. vorax appear to 

 be merely the embiyos, or otherwise the gemmae, of Yorticellina, whilst T. 

 tentaculata is imperfectly known, and -^dll probably always remain a ques- 

 tionable organism. Fui'ther, this author would unite Trichodina with Urocen->- 

 trum into a subfamily of Vorticelhna. 



Lachmann (A. N. H. 1857, xix. p. 119) agrees with Stein in limiting the 

 genus to the two species T. Pedicuhis and T. Mitra, and in rejecting the 

 rest as not Yorticellina at all. According to him, Trichodina Grandinella and 

 T. vorcw are rightly referable to Halteria (Duj.). 



Trichodina tentaculata (x, 227). — 

 Discoid, destitute of the wreath of cilia, 

 but with a fascicidus of vibratile cilia, 



and a stylifonn proboscis. 1-280 



T, Pediculus {Cyclidium Pediculus, M.) 

 = Urceolaria stelUna (Duj.) (x. 228-230 j 

 XXIX. 14, 15, 17). — Depressed, urceolate, 

 and discoid, with a wreath of vibratile 

 cilia anteriorly, and another of short 

 moveable micinate cilia, or hooked setoe, 

 posteriorly. Ehrenberg remarks, " I have 

 fed this species many times with indigo, 

 and have seen numerous stomachs filled 

 with the blue ma,tter. It always runs 

 upon the back, where there is a wreath 

 of 24 to 28 mobile hooks (or uncinate 

 cilia), and has the mouth and vibrating 

 wreath of 48 to 64 cilia directed up- 

 wards." It appears to feed upon the 

 little granules of the body of the Fresh- 

 water Pol}^e (Hi/dra, ' Microscopic Ca- 

 binet,' pi. vii.) (Figs. 228 and 229 are side 

 views, attached to a portion of a poh^pe ; 

 fig. 230 is a top view). 1-570'' to 1-280". 

 T. Pediculus (xxix. 14-17) is described 

 in much detail by Stein (Lifusionsthiere, 

 p. 175). " It has," he writes, " a turban- 

 shaped body ; the truncated conical an- 

 terior segment is morphological with the 

 rotary organ of typical Vorticellina, and 

 is shorter than the very ventricose and 

 expanded posterior segment, from which 

 it is separated by a deep annular con- 

 striction or furrow, occupied by a wreath 

 of vibratile cilia of less length than those 

 forming the posterior zone. The oral 

 aperture is seated in this farrow, the cilia 

 of which are active in impelling food 

 into the mouth. The posterior ciliary 

 zone is parallel with the one in front, 

 j ust described, and occupies the posterior 

 smface of the hindmost segment of the 

 body, near to the line of attachment of 

 the circlet of uncini, as can be best seen 

 when the animal is dead. It is this zone 

 which principally serves for locomotion. 

 The anterior segment can be retracted, 

 and even vanish, by being taken up into 

 the posterior, when the tigure becomes 

 cvlindrical, with abruptly truncate ends. 

 "The posterior segment also contracts it- 



self considerably, and in so doing pre- 

 sents several annular folds. The margin 

 of the truncated extremity, which is 

 much smaller than a section made through 

 the middle of the posterior segment, is 

 fringed by a firm cartilaginous or horny 

 ring, having both on its outer and inner 

 fice a series of uncini, placed at equal 

 distances from each other, and some- 

 what constricted behind the origin of 

 each pair. The inner row of uncini lie 

 in the same plane as the posterior sur- 

 face; but the external row are strongly 

 turned outwards and backwards. Besides 

 these is a structure not hitherto described, 

 consisting of an annular, transparent, 

 elevated rim or collar, often of a slight 

 yellow colour, and of a horny aspect^ 

 placed aroimd the outer margin of the 

 corneous ring, above the base of the 

 outer series of uncini. It is extremely 

 flexible, directed obliquely outwards, and 

 marked by very fine lines. The circlet 

 of hooks is at once dissolved by acetic 

 acid, whilst this structure remains ; and, 

 on the other liand, the whole prehensile 

 apparatus disappears when the animal 

 is put into alcohol." The structm'e of 

 Trichodina, as now imfolded by Stein, 

 was both imperfectly and erroneously 

 conceived by Ehrenberg. 



The long diameter of the largest Tri- 

 chodina Pediculus Stein met with was 

 1-360"; the transverse diameter was 

 about the same. Small specimens oc- 

 curred of only half the size, but complete 

 in all the details of organization. 



T. vorax. — Oblong, cylindrical, or 

 slightly conical ; anterior part convex, 

 and crowned with cilia ; the back rather 

 attenuated and smooth. 1-570". 



This and the next species are, from 

 their dissimilarity to T. Pedicuhis, re- 

 mo^-ed by Dujardin to another genus he 

 names Halteria, — the two being equiva- 

 lent to HalteriaGrandinella, wliich again, 

 in Stein's opinion, is the embryo of an 

 Acinetiform phase of a Vorticella. 



T. GrandineUa (M.).— Nearly spherical; 

 sharply attenuated posteriorly ; a wreath 

 of cilia surrounds the truncated fore part. 



