188 



THE AMERICAN MONTHLY 



[October, 



contour being thus far characteristic. 

 The truncated posterior extremity is 

 apparent only in the largest and pre- 

 sumably the oldest individuals, and 

 not always with even them. Repro- 

 duction is by transverse fission and by 

 encystment with subsequent binary 

 fission, the external cyst wall being 

 smooth. 



Stylonychia vorax^ sp. nov. (Fig. 



lO). 



Body elongate, obovate, more than 

 twice as long as broad, tapering and 

 obtusely pointed, sometimes evenly 

 rounded or obliquely truncate, pos- 

 teriorly ; frontal border prominent, 

 obliquely crescentic ; lateral margins 

 often flattened and parallel ; mar- 

 ginal set£e large, scarcely interrupted 

 posteriorly, those on the left-hand 

 side remote from the body-margin 

 and projecting .only at the posterior 

 extremity ; distal extremities of all 

 the anal styles extending beyond the 

 body-margin ; caudal setae stout, not 

 widely separated, rising from the 

 posterior margin of the body ; peri- 

 stome field extending to the centre of 

 the ventral surface, the right-hand 

 border nearly straight, ciliate and 

 bearing an undulating membrane ; 

 contractile vesicle single, spherical, 

 near the termination of the peri- 

 stome, on the left-hand side ; nucleus 

 double, ovate ; dorsal surface bearing 

 one or more longitudinal rows of 

 short, immotile, hispid setae ; frontal 

 and anal styles often fimbriate. 

 Length of body ^^^ inch. Habitat. 

 — Shallow ponds in early spring. 



This is the smallest member of the 

 genus yet observed, and its "charac- 

 ters are so obviously different from 

 those of pi^eviously recorded species 

 that it is easily recognizable. Two 

 specially noteworthy features are that 

 all the anal styles project beyond the 

 body, and that the caudal setae spring 

 directly from the edge of the posterior 

 border, and not, as in S. mytilus 

 Ehr., S, iiotophora^ and S.putrhza, 

 from the dorsal surface. 



The infusorian is voracious, de- 

 vouring the numerous flagellate or- 



ganisms so abundant in the shallow 

 pools in early spring, until the body 

 becomes not only colored by them, 

 but gorged and often distorted by the 

 internal pressure. It was this re- 

 markable appetite that suggested the 

 specific name. 



Acineta Jluviatilis ^ sp. nov. (Fig. 



Lorica sub-triangvilar, compressed, 

 transparent, thin and delicate ; about 

 one and one-third times as long as 

 broad, widest at the distal border, 

 somewhat constricted anteriorly, 

 thence tapering posteriorly to the 

 pedicel ; lateral borders flattened, the 

 lorica thus presenting a quadrangular 

 outline in horizontal optical section ; 

 frontal margins united anteriorly ex- 

 cept at the two ovate antero-lateral 

 apertures for the passage of the ten- 

 tacles ; pedicel short, not exceeding 

 one-third the length of the lorica, 

 usually slightly widened at the distal 

 extremity ; enclosed zooid generally 

 entirely filling the cavity of the lorica, 

 to which it is attached at the posterior 

 extremity and apparently by the en- 

 tire lateral surface ; endoplasm granii- 

 lar ; tentacles distinctly capitate, in 

 two antero-lateral fascicles ; contrac- 

 tile vesicle single, spherical, anterior- 

 ly situated ; nucleus ovate or broadly 

 subspherical, conspicuous, subcen- 

 trally located. Length of lorica 

 7^"(r to -^^ inch. Habitat. — On Val- 

 lisneria spiralis from a tide-water 

 creek. 



This may be regarded as the con- 

 necting link between the marine 

 Acineta tuberosa, Ehr., and the 

 fresh water A. lemnar?im Stein, both 

 of which it resembles in the form of 

 the lorica. Its systematic position is 

 evidently between these species. 

 From A. tuber osa it conspicuously 

 differs in the short pedicel, the ap- 

 parent adhesion of the entire body to 

 the internal walls of the lorica, ex- 

 cept at the anterior or distal border, 

 and by its fresh-water habitat. The 

 irregularly quadrilateral outline of 

 the loricae in horizontal optical sec- 

 tion are similar, as well as the habit. 



