7 10 ORDER PERITRICHA. 



Professor H. James-Clark. The Epistylis vegetans of the same writer : " Bodies 

 very small, ovate, disposed in clusters on a branched yellow pedicle ; length 

 1-3450", is synonymous with Anthophysa Muelleri" A third species, Ehrenberg's 

 Epistylis arabica " Small, oval, campanulate, pedicle but little branched, smooth 

 and hyaline; entire height 1-140"; hab. Red Sea" is probably a Flagellate form 

 belonging to the genus Codosiga, nearly related to the author's C. pyriformis. The 

 Epistylis minutus of R. Greeff,* whose colony-stocks resemble in miniature those 

 of Ep. flavicans, but the length of whose bodies does not exceed 1-3000", is appa- 

 rently referable to the genus Dendromonas. 



GENUS XI. OPERCULARIA, Stein. 



Animalcules ovate, pyriform, or campanulate, seated at the extremities 

 of a rigid, more or less branching, tree-like pedicle or zoodendrium ; ciliary 

 disc attached to one side of the wide oral entrance or vestibulum, isolated 

 and usually elevated to a considerable distance above the margin of the 

 peristome, after the manner of an operculum ; a delicate hyaline collarlike 

 membrane taking its origin from the inner border of the peristome, usually 

 protruded with and forming a sort of under-lip to the ciliary disc ; other 

 g tructural details as in Epistylis or Vorticella. 



The rigid, mostly ramifying pedicle of the members of this genus corresponds 

 essentially with that of Epistylis, but the animalcules attached to the summits of 

 the branches are readily distinguished by the more complex structure of their oral 

 or peristomal region. In the lateral attachment and operculum-like elevation of the 

 ciliary disc the zooids of Opercularia also considerably resemble those of the genus 

 Lagenophrys, while the membranous collar-like expansion, forming as it were a 

 supplementary under-lip to the ciliary region, represented feebly in Lagenophrys, may 

 certainly be accepted as homologous with the more complex funnel-like membrane 

 of the genus Spirochona, An additional feature which serves to indicate the affinity 

 of Opercularia with Lagenophrys is the usually more hardened texture of the cuticular 

 membrane, which in many instances is indurated to such an extent as to remain as 

 a distinct chitinous shell after the decomposition of the soft interior. These two 

 genera thus prepare a passage to the distinct shell-producing or loricate Vorticellan 

 types Cothurnia and Vaginicola. 



When first instituted by Stein, the presence of two sorts of zooids, as occurs 

 frequently in the genus Zoothamnium, was included among the points for diagnosis ; 

 more recent investigation has, however, demonstrated that the supposed secondary 

 zooids were merely parasitic or commensal Acinetce. All the species of Opercularia 

 so far discovered are inhabitants of fresh water, and are for the most part met with 

 attached to various aquatic insects and Entomostraca. 



Opercularia nutans, Ehr. sp. PL. XXXIX. FIGS. 22 AND 23. 



Bodies ovate or attenuate fusiform, about two and a half times as long 

 as broad, tapering towards each extremity, the anterior end the wider, 

 the posterior one often transversely plicate; ciliary disc considerably 

 elevated above the margin of the peristome, bearing two circlets of 

 cilia ; membranous collar largely developed, obliquely set ; endoplast band- 

 like, curved ; pedicle tree-like, slender, branching profusely and dichoto- 

 mously, attaining a considerable proportionate altitude, distinctly annulate 



* ' Wiegmann's Archiv,' Bd. xxxvii., 1871. 



