GENUS ME TA C YSTIS—PERISPIRA^ANOPHR YS. 511 



animalcules occupy a permanent position within the vital fluid of the mammal 

 named, further corroborative testimony in the same direction is much to be 

 desired. 



Genus II. METACYSTIS, Cohn. 



Animalcules free-swimming, symmetrically ovate or elongate, persistent 

 in form ; the entire cuticular surface clothed with fine vibratile cilia, with 

 the exception of a bare vesicular-like posterior portion ; oral aperture 

 anteriorly situated, encircled by a fringe of stouter cilia. 



Metacystis truncata, Cohn. Pl. XXVII. Figs. 11-13. 



Body ovate or elongate, subcylindrical, the posterior third or fourth 

 smooth and vesicular-like, the remaining portion transversely annulate, and 

 finely ciliate ; the anterior extremity abruptly truncate, bearing a circlet of 

 long, incurved cilia ; endoplast spherical, central. Length of most elongate 

 specimens 1-900". Hab. — Salt water, among decaying algae. 



As recognized by Cohn in his description given of this species,* it would seem 

 by no means improbable that it is identical with the marine type figured and 

 described by O. F. Miiller f under the title of Trichoda paxillus, but which does 

 not appear to have been encountered by any subsequent observer. 



Genus III. PERISPIRA, Stein. 



Animalcules free-swimming, symmetrically ovate, persistent in shape 



but not encuirassed ; oral aperture at the anterior extremity ; cuticular surface 



entirely and finely ciliate; a raised border, bearing the adoral cilia, 



extending in a spiral manner from the anterior extremity round the body 



towards the posterior end ; anal aperture and contractile vesicle postero- 



terminal. 



Perispira ovum, Stein. Pl. XXVII. Fig. 18 (?). 



Body ovate, longitudinally striate, about twice as long as broad, oral 

 aperture presenting the form of a transverse fissure; endoplasm usually 

 filled with chlorophyll-granules. Dimensions unrecorded. 



Hab. — Fresh water. 



Stein suggests that this species is possibly identical with the Holophryoa vum of 

 Ehrenberg; the elastic character of the parenchyma and cuticular covering in that 

 type, as compared with Stein's diagnosis, would seem, however, to scarcely favour this 

 interpretation. The accompanying figure, Pl. XXVII. Fig. 18, represents an ani- 

 malcule apparently closely allied to it if not identical with Stein's species, delineated 

 in the manuscript notes of Bombay Infusoria kindly placed at the author's 

 disposal by Mr. Carter ; the conspicuously larger size of the adoral spire of cilia 

 affords perhaps sufficient grounds for its recognition as a second species of the 

 genus Perispira. 



Genus IV. ANOPHRYS, Cohn. 



Animalcules free-swimming, persistent in shape but highly flexible, 

 elongate-ovate, rounded posteriorly, the anterior extremity pointed, more or 



* " Neue Infusorien im Seeaquarium," ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xvi., 1866. 

 t 'Animalcula Infusoria,' 1786. 



