6; 8 ORDER PERITRICHA. 



of the body in advance of each of these sulci overlapping the preceding 

 one after the manner of a telescope ; pedicle slender, scarcely exceeding 

 the body in length, contracting spirally. Length of body 1-500". 

 HAB. Fresh water, solitary. 



Obtained sparingly from pond water, in October 1872, in company with Vorticclla 

 longifilum. 



** Bodies broadly campamilate. 



Vorticella campanula, Ehr. 

 PL. XXXIV. FIG. 36, AND PL. XLIX. FIG. 12. 



Body usually broadly campanulate or hemispherical, but soft and 

 very variable in contour ; subspheroidal, with a puckered anterior margin 

 when contracted ; the frontal margin widely dilated, often exceeding in 

 width the length of the body; the ciliary wreath apparently forming two 

 or more spiral convolutions ; pedicle thick, varying from three or four to six 

 or seven times the length of the body ; cuticular surface smooth, highly 

 elastic; parenchyma densely granular centrally. Length of body 1250" 

 to i 120". HAB. Pond water, social. 



The zooids of this species are clearly visible to the unaided eye, and often 

 occur in such abundance as to conspicuously cover the surface of submerged leaves 

 or other objects in the form of a thick bluish-white slime. A characteristic by 

 which, as pointed out by D'Udekem, this type may be easily recognized, is fur- 

 nished by the densely granular consistence of the internal parenchyma, which im- 

 parts to the central region of the body, when viewed with transmitted light, a black 

 and opaque aspect. It would seem probable, as anticipated by Ehrenberg, that the 

 Vorticella lunaris of O. F. Miiller, PI. XLIX. Fig. 42, is identical with this species. 



In none of the numerous examples examined by the present author has the 

 larger size, quoted from Ehrenberg in the foregoing diagnosis, been encountered, 

 that of 1-250" to 1-200" being most dominant, and such dimensions being 

 considerably inferior to those of V. spedabilis, described later on. 



Vorticella citrina, Ehr. PL. XXXV. FIG. 29, AND PL. XLIX. FIG. 13. 



Animalcules broadly campanulate, hemispherical, plastic and changeable 

 in form, the frontal border much dilated, crateriform, often considerably 

 exceeding in diameter the entire length of the body; depressed with a 

 puckered anterior border when contracted; parenchyma transparent, 

 usually pale yellow ; cuticular surface smooth ; pedicle slender, four or five 

 times longer than the body. Length 1-430" to 216". 



HAB. Fresh water, on Lemna and various aquatic plants, social. 



This species represents one of the most abundant fresh-water types. In the 

 plasticity of. the parenchyma and capacity to assume a great variety of contours, it 

 rivals the form last described, while in the patellate or crateriform expansion of the 

 peristome-border it more nearly approaches Vorticella hemisphcerica and V. patellina. 

 In its contracted state the body of this animalcule, as observed by the author, 

 exhibits a very characteristic contour; the anterior margin in all these instances 

 assuming a more or less lobate or puckered aspect, while the body as a whole some- 

 times retains a subspheroidal form, but more often presents a much depressed melon- 

 or tomato-like outline. Under a magnification of three or four hundred diameters, 



