GEA'US OPHRVDIUM. 735 



the similarity that subsists between the animalcules of this species and the detached 

 zooids of Oph/yJium, a still more marked one perhaps exists between the same and 

 the permanently attached naked animalcules of D'Udekem's Gerda fixa previously 

 described. 



Genus XXI. OPHRYDIUM, Ehrenberg. 



Animalcules elongate, subcylindrical, highly contractile, growing in 

 attached or free-floating social clusters, and exuding a common coalescent 

 mucilaginous investing matrix or zoocytium, within which the bodies are with- 

 drawn at the time of contraction, generally united to each other or to their 

 basis of support by a simple or branching pedicle, but occasionally sessile; 

 peristome and adoral system as in the ordinary Vorticellids ; ciliary disc 

 on the oral or ventral side usually greatly elevated ; contractile vesicle 

 spherical, subcentral, with a canal-like diverticulum, which ascends to and 

 surrounds the peristome; cndoplast elongate, cord-like, often convolute. 

 Inhabiting salt and fresh water. Increasing normall}' by longitudinal, but 

 occasionally by transverse fission. 



By many writers Ophrydium has been separated from the ordinary VorticellidK, 

 and been made the type of a distinct family group under the title of the Ophrydina. 

 It is evident, however, that its distinctive feature, as represented by the common 

 mucilaginous matrix, may be regarded as a com[)ound modification only of the lorica 

 of Vaginicola and its allies, being in conjunction with that more indurated structure 

 derived through a redundant development of or exudation from the hyaline cuticle. 

 The passage from one group to the other is moreover clearly indicated through the 

 newly introduced genus Ophiondla, the sheath of which permanently retains the soft 

 and plastic consistence characteristic of the lorica of Vagiiiicola in its earliest or 

 immature condition. An essentially analogous socially constructed mucilaginous 

 matrix or zoocytium has been already described in connection with the several 

 Flagellate genera Phalansteriiim, Spongomonas, and Proterospongia, and in the author's 

 opinion obtains also, with various complex modifications, throughout the entire class 

 of the Spongida. A further reference to this premised analog)' is included in vol. i. 

 pp. 171 and 176. 



Ophrydium versatile, Miill. sp. Pl. XLI. Figs. 1-9. 



Bodies flask-shaped, ovate or globular when contracted, attenuate 

 when extended, usually exhibiting a slightly inflated, subfusiform central 

 portion, a conically pointed posterior extremity, and a cylindrical and 

 neck-like anterior region ; the cuticular surface finely annulate throughout 

 and also longitudinally plicate towards the posterior region ; vestibular fossa 

 very capacious, occupying the entire space between the highly elevated 

 ciliary disc and border of the peristome, continued into a wide ciliated 

 pharynx, and terminating in an elongate oesophagus, the entrance to which 

 is dilated and double-walled, and thence developed backwards to the centre 

 of the body as a narrow and, except when food is passing, scarcely 

 visible tube ; parenchyma coloured more or less brilliant green through the 

 presence of innumerable imbedded chlorophyll-granules ; zooids forming 

 extensive and mostly free-floating social clusters of a more or less globose 



