7 1 4 ORDER PERITRICHA. 



This species is distinguished by its discoverer, A. Wrzesniowski,* from 0. ber- 

 bcrhia, which it most nearly approaches, by the abruptly truncate non-contracted 

 anterior border, by the closely striate pedicle, and by the less considerable develop- 

 ment of the vestibular cleft ; the endoplast is likewise much more elongate. 



Opercularia hospes, From. sp. Pl. XXXIX. Figs. 9-1 i. 



Bodies clavate, about two and a half times as long as broad, the peri- 

 stome-border widest, the posterior end attenuate ; ciliary disc large, mode- 

 rately elevated ; membranous collar conspicuous, obliquely set ; the whole 

 surface of the body covered with minute fibrillae, which, whether belonging 

 to the organism or of a parasitic nature, has yet to be determined ; pedicle 

 stout, cylindrical, punctate. Length of bodies 1-200". 



Hab. — Fresh water. 



This species is founded upon the type described by Fromentel t under the title of 

 Epistylis hospes, but which, as is shown by both his drawings and description, is a 

 true Opercularia. The membranous collar, as represented by him in outline, he takes 

 for the vestibular bristle of an ordinary Epistylis bent round upon itself. The 

 singular fibrillate structures with which the surface of the body is invested are 

 regarded by Fromentel as possibly constituted of minute parasitic growths, but their 

 extreme abundance and equal distribution in every specimen examined scarcely 

 supports his view. Each distinct fibrilla is characterized as hair-like, with a globular 

 head, but the general aspect conveyed by Fromentel's figures, here reproduced, is 

 that of a froth-like exudation, or it may be a layer of trichocysts. It is to be 

 regretted that no details are given as to habitat, the proportions and form of growth 

 of the pedicle, or whether its ramifications support a large or small number of zooids. 

 The small portion of this element figured exhibits a remarkable punctate character. 



Sub-Family II. VAGINICOLINA. 



Animalcules excreting and inhabiting indurated sheaths or loricse. 



Genus XII. VAGINICOLA, Lamarck. 



Animalcules elongate-subcylindrical, enclosed singly or in pairs within 

 an indurated vase-shaped sheath or lorica, to the bottom of which they are 

 affixed directly, or by means of a short pedicle ; lorica erect, attached by 

 its posterior margin to the selected fulcrum of support, in a sessile 

 manner, or through the medium of an exceedingly short, rudimentary, rigid 

 pedicle ; oral and ciliary system as in Vorticella ; increasing by longitudinal 

 fission or gemmation ; in the former instance the zooids temporarily occupy- 

 ing the same domicile. Inhabiting salt and fresh water. 



The genus Vaginicola, since the date of its first institution by Lamarck and further 

 extension at the hands of Ehrenberg, Dujardin, Stein, Claparede and Lachmann, and 

 other more recent writers, has become so unwieldy in point of numbers, that its 

 subdivision into a plurality of generic groups, each possessing well-marked structural 

 characteristics, has been decided on and will materially assist the student in his 



* ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xx., 1870. 

 t ' Etudes sur les Microzoaires,' Paris, 1876. 



