1885.] ->& [Stokes. 



contractile vesicle of the former, have not been previously noticed, while 

 a moniliforrn nucleus is thus far restricted to H. similis. 



Holosticha caudata, sp. nov. (Fig. 5). Body elongate, eight times as 

 long as broad, soft and flexible, widest centrally, constricted near the 

 apical extremity of the peristome-field, widened anteriorly, tapering pos- 

 teriorly in a tail-like prolongation, the tip somewhat dilated and curved 

 toward the right-band side ; anterior border rounded, lip narrow, cres- 

 centic ; frontal styles three ; ventral setae in two straight median rows, 

 those on the right-hand side largest ; anal styles five, slender, the extremi- 

 ties often fimbriated ; marginal setae numerous, large, flattened, projecting 

 and most abundantly developed at the posterior border ; peristome-field 

 confined to the anterior one-fifth of the ventral surface, the right-hand 

 margin finely ciliate and bearing an undulating membrane ; contractile 

 vesicle single, spherical, near the left-hand side of the apical extremity of 

 the peristome ; anal aperture dorsal near the beginning of the tail-like 

 prolongation ; immotile dorsal hispid setae numerous, long and fine. 

 Length of body 1-50 inch. Habitat. — Marsh water, with Sphagnum. 



In Holosticha hymenophora (Fig. 6), a sub-terminal anal aperture exists 

 and has been noticed several times, but whether on the ventral or dorsal 

 surface was impossible to positively determine, as the Infusorian in each 

 instance happened to be rapidly rotating on the long diameter, and the 

 aperture opened and closed before the focus could be changed. My im- 

 pression, however, is that it is dorsal, and I have no hesitation in predict- 

 ing that the cytopyge will be observed in that position, not only among 

 those described in this paper where the dorsal position is the rule, but with 

 many of the Hypotricha, even with those common and seemingly best- 

 known forms in which so important a structural point ought to have been 

 observed long ago. An instance occurs in Oxytricha platystoma (Ehr.) 

 S. K., where the writer has seen the anal aperture on the dorsal surface at 

 the left-hand side of the median line and some distance from the posterior 

 extremity. That it should become developed on the upper surface is cer- 

 tainly a satisfactory and a beautiful adaptation. The lower aspect is 

 needed for the support of the ambulatory organs and anal styles, the pos- 

 terior extremity is occupied by a luxuriant growth of marginal setae, with 

 usually one or more supplementary rows of similar appendages, while the 

 dorsum is either entirely naked or only the bearer of immotile hispid hairs, 

 which can be temporarily crowded out of position, or even permanently 

 displaced, without inconvenience or injury to the Infusorian. 



Holosticha hymenophora, sp. nov. (Fig. 6). Body elliptical, three to four 

 times as long as broad, soft, flexible and somewhat extensile, narrowed 

 anteriorly and slightly curved toward the left-hand side ; lip prominent, 

 crescentic ; frontal styles five ; ventral setae in two straight closely approx- 

 imated median rows ; the left-hand series beginning at the apical extremity 

 of the peristome ; anal styles five, straight, slender, in an oblique row, the 

 first or right-hand one slightly projecting beyond the body ; marginal setae 

 longest and projecting posteriorly ; peristome-field extending for one-third 



PROC. AMER. PHILOS. SOC. XXIII. 121. D. PRINTED OCTOBER 10, 1885. 



