GENUS A CIXE TA. 8 3 I 



essentially in its smaller dimensions and in the character of the posterior region of 

 the body, which is never contracted, quadrangular and distinctly adherent to the 

 lorica, as obtains in that type. In common with many other representatives of the 

 present genus, A. lemnarum was originally described by Stein as the immature or 

 " Acinete " condition only of some higher Peritrichous Ciliate Infusorium, the 

 habitat of this particular type inducing him to regard it as a transitional form of 

 either Vortkdla jicbuUfcra or Epistylis {Opercularia) nutans. Having satisfied him- 

 self later on that these Acinetae hold a substantial claim for independent recognition, 

 the title here applied was conferred upon it. The author has recently received 

 examples of this species from Mr. Thomas Bolton, of Birmingham, growing, in 

 company with BenJrosoma radians, Acineta grandis, and A. mystacina var. longipes, 

 on various aquatic plants. 



Acineta grandis, S. K. Pl. XLVIII. Fig. 24. 



Lorica subtriangular, compressed, widest at the anterior border, tapering 

 gradually towards the posterior extremity, communicating externally by 

 a cleft-like aperture, which extends throughout the entire length of the 

 anterior border ; pedicle slender, rectilinear, three or four times the length 

 of the lorica ; enclosed animalcule ovate or elliptical, usually occupying the 

 anterior half or an even less considerable area of the cavity of the lorica ; 

 tentacles distinctly capitate, very numerous, forming two antero-lateral 

 bundles ; contractile vesicle spherical, subcentral ; endoplast band-like, ren- 

 dered conspicuously visible only by the action of reagents ; parenchyma 

 transparent, finely granular. Length of lorica l-ioo" to I-75". 



Hab. — Fresh water, on Anacharis, Nitella, and Potamogeton: Birming- 

 ham and Stratford Canal. 



Examples of this new and handsome species have been remitted to the author in 

 November of the two consecutive years 1880 and 1881. While at first sight it 

 would appear to diff"er but little, except in size, from the respective salt- and fresh- 

 water forms Acineta tuberosa and A. lemnarum, it is found, on closer inspection, to 

 yield many distinctive features. The lorica, in the first place, has a much more 

 simple structure, it being freely open throughout the anterior margin, in place of being 

 arched over by a continuation of its lateral walls, leaving slit-like apertures only for 

 the extrusion of the tentacles, as obtains in those two forms. The body of the 

 animalcule is finally of much less relative size, it usually occupying, as shown in the 

 accompanying figure, scarcely one-half of the cavity of its protective sheath, and 

 adhering to it only by its frontal border. The comparatively colossal dimensions of 

 this species, as compared with its homotype Acineta lemnarum, found grou'ing close 

 beside it, is well illustrated in the same drawing, and where, at a, an outline of the 

 more familiar but smaller species has been added for the purpose of comparison. 

 Although the form and position of the nucleus or endoplast was not readily 

 detected in living specimens, this structure was rendered distinctly visible in 

 examples killed with osmic acid and then treated with picrocarmine. 



Acineta linguifera, C. & L. Pl. XLVI. Figs. 36-39. 

 Lorica subtriangular, compressed, tapering posteriorly, developed 

 anteriorly into two everted, bilaterally even, lip-like expansions, frequently 

 annulate transversely, each annulation representing a new cycle of growth ; 

 pedicle very short; body filling the entire cavity of the lorica, and adherent 

 to it, projecting in a tongue-like form beyond the anterior margin, bearing 



