102 Dr. A. C. Stokes on some 



the anterior extremity recurved towards the ventral surface, 

 the ovate oral aperture placed in the ventral concavity thus 

 formed ; cuticular surface longitudinally striate j pharynx short, 

 recurved, the roof bearing a series of tine cilia, longest ante- 

 riorly, and projecting beyond the oral aperture ; contractile 

 vesicle single, spherical, posteriorly placed near the ventral 

 surface ; nucleus single, subspherical, and subcentral. Length 

 of body -j^ir ii^ch. 



Hab. Standing water, with dead leaves. Movements 

 rapid. 



The pharyngeal ciliation seems to be confined to the superior 

 wall or roof. The cilia are very fine, and usually vibrate 

 synchronously, thus presenting so close a resemblance to an 

 undulating membrane, that their character can be satisfac^ 

 torily determined only when the infusorian is in a dying 

 condition. 



Amphileptus monilatus, sp. nov. (PI. I. fig. 9.) 



Body elongate, subfusiform, about fifteen times as long as 

 broad, the dorsal surface flattened, the ventral convex, the 

 anterior trunk-like portion forming one fourth of the entire 

 leno-th of the body ; the posterior attenuate tail-like part 

 about one sixth of that length, the trunk bearing a fringe of 

 larger cilia on its lower surface, and an even inferior row of 

 trichocysts; contractile vesicles small, numerous, in a single 

 series along the dorsal border, but not extending into the 

 posterior attenuation ; nucleus moniliform, the nodules small, 

 ovate ; pharnyx conical, finely plicate ; anal aperture at the 

 base of the caudal prolongation. Length of body ^ inch. 



Hab. Still water, with Cerato2)hyllum and Utricularia. 



Li general appearance this Lifusorian closely resembles A. 

 qigas^ C. & L., differing chiefly in the shorter trunk, and espe- 

 cially in the moniliform nucleus, the latter, in A. gigas^ being 

 band-like. 



In connexion with A. gigas I have been able to verify the 

 statement of Wrzesniowski, that reproduction takes place by 

 oblique central fission. The first noticeable change in the 

 appearance of the body is the development of an obliquely di- 

 rected subcentral ridge apparently surrounding the animalcule. 

 The division is rapid, the anterior portion of the posterior 

 moiety being very obliquely truncate and finally developing 

 into the trunk ; the posterior surface of the anterior part being 

 evenly rounded immediately after fission. The oral aperture 

 and conical pharynx are formed in the posteriorly separating 

 moiety before the final division of the two individuals. Con- 

 juo-ation has been observed with a form whicli I have identified 



