GENUS VORTICELLA. 685 



about and selecting a site for the initiation of its independent sedentary life, another 

 hour elapsing between this and its development of a pedicle and the disappearance 

 and absorption of the posterior circlet of locomotive cilia. During its nomadic 

 existence the animalcule expended a considerable interval in creeping, after the 

 manner of a Trichodina, over the surface of the glass slide and algoid filaments 

 with the aid of its flattened posterior extremity and associated wreath of cilia, and 

 which for the nonce fulfilled all the essential purposes of the complex acetabuliform 

 organ of the last-named genus. The species figured by Mereschkowsky in his 

 ' Protozoa of Northern Russia,* under the name of Vorticella pyrum, must be 

 regarded as a local variety only of the present type. The examples there figured, 

 as found attached to algae and hydroid zoophytes in the White Sea, differ from the 

 present form merely in the greater relative length of the pedicle, which equals three 

 or four times that of the body ; the contour of the body, together with its charac- 

 teristic striation, is otherwise essentially identical. 



Vorticella marina, Greeff. 

 PL. XXXV. FIGS. 1-8, AND PL. XLIX. FIG. 30. 



Body conical, campanulate, tapering posteriorly, slightly constricted 

 beneath the peristome, about one and a half times as long as broad ; 

 peristome-border thick, dilated and revolute, ciliary disc moderately 

 elevated ; cuticular surface distinctly and coarsely striate transversely ; 

 pedicle somewhat thick, four or five times the length of the body, con- 

 tracting spirally. Length 1-375". 



HAB. Salt water, scattered or in small social groups. 



This species, described by Greeff,t has been obtained by the author both at 

 Bognor, Sussex, in August 1872, and also attached to the algae and zoophytes on the 

 Jersey coast. From the Vorticella striata of Dujardin, which it to some extent re- 

 sembles, it may be distinguished by the considerably more dilated and revolute 

 character of the peristome-border. The conjugation of the more minute migrant 

 zooids with the sedentary individuals forms the especial subject of Greeff 's account 

 of the species, and has been referred to in detail in the general account given on 

 a preceding page of the reproductive phenomena of the genus Vorticella. 



Vorticella quadrangularis, S. K. 

 PL. XXXIV. FIG. 34, AND PL. XLIX. FIG. 31. 



Body attenuate, subcylindrical, three and a half time* as long as broad, 

 tapering posteriorly, with a projecting angle at within a short distance of 

 both the anterior and posterior extremities, faintly striate transversely, 

 slightly constricted beneath the peristome, ciliary disc projecting hemi- 

 spherically above the border of the peristome ; pedicle slender, compara- 

 tively short, about one and a half times longer than the body. Length of 

 body 1-125". HAB. Pond water ; social. 



In proportion to its width, the present species represents the most attenuate 

 representative of the genus yet recorded. The specimens from which the accom- 

 panying figures and description are derived were found growing on Myriophyllum 

 in pond water derived from the neighbourhood of Stoke Newington, London, in 

 September 1871. ^__ 



* 'Archiv fur Mikroskopische Anatomic,' Dec. 1878. 

 t Wiegmann's ' Archiv fur Naturgeschichte," 1871. 



