GENUS LEPTOMONAS. 243 



Cyathomonas emarginata, From. 



Body elongate, subcylindrical, slightly tapering posteriorly, the anterior 

 border truncate, notched or emarginate on one side ; flagellum long and 

 slender, nearly twice the length of the body ; parenchyma clear yellow, 

 with red granules interspersed ; contractile vesicle conspicuous, situated in 

 the posterior third of the body. Length of body i-iooo". 



HAB. Fresh water. 



Cyathomonas elongata, From. 



Body elongate, about two and a half times as long as broad, tapering 

 posteriorly, slightly constricted immediately behind the truncate anterior 

 border; flagellum long and slender; parenchyma clear yellow, enclosing 

 a few red granules ; contractile vesicle situated in the .posterior third of the 

 body. Length 1 800". HAB. Fresh water. 



The distinction between this and the preceding type is apparently insufficient for 

 their specific separation. 



GENUS IV. LEPTOMONAS, S. K. 

 (Greek, leptos, slender ; monas.) 



Animalcules free-swimming, persistent in shape, elongate fusiform or 

 aciculate, bearing a single long undulating flagellum at the anterior 

 extremity ; no distinct oral aperture yet detected. 



The above generic title combined with the following specific one is here intro- 

 duced for the reception of the monoflagellate animalcule figured and briefly described, 

 without any name, by O. Biitschli in the ' Zeitschrift fur Wissenschaftliche Zoologie,' 

 Bd. xxx. Hft. ii., for January 1878. While corresponding with the ordinary repre- 

 sentatives of the genus Monas in its simple monoflagellate type of structure, it is to 

 be distinguished from them by its persistent acicular form. From what little is at 

 present known of it, it is almost impossible to decide whether this organism possesses 

 a sound claim to the separate generic distinction here accorded it, or whether it is 

 not the developmental phase of some other flagellate species. It was originally 

 proposed to employ the generic title of Rhaphimonas with referen :e to its acicular 

 contour for the distinction of this specific form. The contemporary adoption of 

 the almost identical one of Raphidomonas by Stein, in connection with the Monas 

 semen of Ehrenberg, has, however, made it desirable to substitute a new name for 

 the present form. By accident, the previously selected title has been employed by 

 the author in an article on parasitic Infusoria contributed to the ' Popular Science 

 Review' for October 1880. 



Leptomonas Butschlii, S. K. PL. XIII. FIGS. 25 AND 26. 

 Body elongate fusiform, pointed at each extremity, but most attenuate 

 posteriorly, eight or nine times as long as broad ; flagellum nearly twice the 

 length of the body ; a contractile vesicle situated at a short distance from 

 the anterior extremity, and a little behind this a dark, granular, nucleus-like 

 body. Length 1-2250". 



HAB. Parasitic, within the intestinal tract of the Nematozoon Trilobus 

 gracilis, 



R 2 



