GENUS VORTICELLA. 673 



the one containing those forms in which the cuticular surface is smooth or glabrous, 

 and the other those in which with the moderate magnification of three or four 

 hundred diameters only, transverse striae or other surface ornamentations are clearly- 

 perceptible. Both of these two sections admit of subdivision into subordinate groups 

 based upon the contour of the body of the zooids as presented in their most typical 

 or fully expanded state. Among the most abundant smooth cuticled series it will 

 be found that the body exhibits three leading modifications. In the first of these it 

 is simply ovate or elongate, having a length equalling at least hvice that of the 

 greatest width, while the frontal margin is but slightly dilated. The characteristic 

 features of this series attain their highest development in such forms as V. cucuUiis 

 and V. quaih-angidaris. In the second series the body is normally broadly cam- 

 panulate or bell-shaped, having the frontal margin much dilated, and often exceeding 

 in diameter the longitudinal measurement of the animalcule. The Vorticdla cam- 

 panula of Ehrenberg typifies this section, the V. dtrina and V. patellina affording 

 further examples of this group in which the peristome-border is dilated to such an 

 extent as to approach a contour to which in botanical terminology the title of 

 "h}^ocrateriform" would be appHed. In a third, and as at present known, not very 

 extensive series, fidy t)-pified in the recently described Vorticdla spherica of D'Ude- 

 kem, the body in its most complete state of expansion presents an almost perfectly 

 spheroidal contour. In that section, distinguished by the striate or otherwise ornate 

 character of the cuticular surface, no representative of the spheroidal series has been 

 as yet recorded, while the Vorticdla dongata and V. appuncta of De Fromentel may be 

 cited respectively as characteristic examples of the elongate-conical and broadly cam- 

 panulate groups. To the last-named series has also to be relegated the Vorticdla 

 monilata of Tatem, remarkable for the bead-like elevations which replace the simple 

 striae of the more ordinary species. That in many instances the several groups as 

 above distinguished, and more especially the conical and campanulate series, closely 

 approach and amalgamate with one another, is readily admitted, a hard and fast line 

 of separation being indeed entirely arbitrary and artificial. Applied, however, in 

 its broad sense, and aided by the special characteristics noted in the technical 

 diagnoses, the recognition and identification of the various specific forms, with the 

 assistance of this scheme, is greatly facilitated. 



For the future guidance of investigators of this exceedingly attractive generic 

 group, attention may be profitably directed to the very incomplete data from which 

 in many cases the specific descriptions given in this treatise have been framed, 

 and to which it is exceedingly desirable that more comprehensive details should be 

 added. The large number of new species recently introduced by De Fromentel * 

 are particularly unsatisfactory in this respect. In not a single instance does he 

 record whether the animalcule figured is social or solitary in its habits, whether a 

 denizen of ponds, running water, or infusions, while in but few instances even is 

 the comparative length of the supporting pedicle indicated in his drawings or 

 mentioned in the accompanying text. All of these characteristics are of high 

 importance, and should be registered in drawing up an account of a doubtful or 

 supposed new species. The form assumed by the body in its contracted state 

 should likewise receive attention, this phase, as exemplified in Vorticdla citrina and 

 V. telescopica, often yielding data of as high value for specific discrimination as those 

 afforded by the fully expanded zooids. 



A. — Cuticular Surface Smooth. 



* Bodies conical or elongate. 



Vorticella nebulifera, Ehr. 

 Pl. XXXIV. Fig. 20, Pl. XXXV. Figs. 32-47, and Pl. XLIX. Fig. i. 



Body when extended conical-campanulate, somewhat gibbous, about 

 three times as long as broad, tapering posteriorly, slightly constricted 



* 'Etudes sur les Microzoaires,' 1S76. 



VOL. n. p 



