GENUS GERDA. 657 



manifested, as already observed, in such types as Operciilaria jiuians and O. bcrhcrina. 

 In all the loricate species the sheath or lorica is in its earliest state soft and gelatin- 

 ous, this transient state, considerably exaggerated, characterizing the permanent 

 condition of the mucilaginous habitations of Ophionella and Ophrydium. The 

 highly interesting data connected with the more recently observed reproductive 

 phenomena of this family group are detailed at length in the account given of the 

 representative genus Vorticclla. 



Sub-Family I. VORTICELLINA. 



Animalcules naked, neither inhabiting sheaths or loricae, nor immersed 

 within a mucilaginous investment. 



Genus I. GERDA, C. & L. 



Animalcules solitary, elongate, subcylindrical, recumbent upon or simply 

 adherent to submerged bodies, not possessing a distinct sucker or special- 

 ized organ of attachment as in the genus Scyphidia ; oral system including 

 a peristomal border, vestibulum, and ciliary disc, as in the ordinary Vorti- 

 cella. Increasing by longitudinal fission. Inhabiting fresh water. 



To the single species referred to this generic group by Clapar^de and Lachmann, 

 a second form has been recently added by D'Udeivem. 



Gerda glans, C. & L. Pl. XXXIII. Figs. 36-38. 



Body elongate, subcylindrical, highly contractile, three or four times as 

 long as broad, the wider posterior region, during contraction, assuming 

 with reference to the then conical anterior part a cup-like form ; surface of 

 the inte^-ument above this posterior portion transversely striate ; oral aper- 

 ture narrow, pharyngeal cleft deeply prolonged ; cndoplast ribbon-like, 

 placed longitudinally ; contractile vesicle spherical, posteriorly situated, 

 giving off a slender, canal-like ramification, occasionally branching a second 

 time, which extends to within a short distance of the ciliary disc. Length 

 of extended body 1-125". 



Hab. — Fresh water, among vegetable debris: near Berlin (C. & L.). 



Among the more interesting features of this singular type may be mentioned the 

 position and structure of the contractile vesicle, its posterior situation being the 

 converse of what obtains among all the more ordinary members of the Vorticellidan 

 group, while its canal-like diverticulum finds a counterpart only in the genus Opluy- 

 diiim! Although usually found by Claparede and Lachmann lying about among 

 water plants and vegetable debris, this animalcule was occasionally observed, as 

 fhown at PI. XXXIII. Fig. 38, to develop a posterior circlet of cilia, and to progress 

 through the water after the manner of a detached VortUdla. 



Gerda fixa, D'Udk. Pl. XXXIII. Figs. 34 and 35. 



Body elongate, its surface entirely smooth, the length when extended 

 equalling five or six times that of the greatest breadth ; the posterior third 

 inflated, tapering abruptly and terminating in a blunt point, the two ante- 

 rior thirds narrower, subcylindrical ; peristome-border thickened, reflected ; 



VOL. II. O 



