2 60 ORDER FLAGELLATA-PANTOSTOMATA. 



considerable resemblance to the permanently repent form Reptomonas caudata, pre- 

 viously described. In another example, delineated by Professor Stein, the animalcule 

 encloses within the substance of its parenchyma a recently-devoured spore-like 

 corpuscle. Multiplication by longitudinal fission, preceded by the development, in 

 the first instance, of a second anterior flagellum and caudal filament, is likewise 

 represented in Stein's figures here reproduced. 



Cercomonas crassicauda, Stein. PL. XIV. FIGS. 15 AND 16. 



Body elongate-ovate, from two to two and a half times as long as broad, 

 its substance granulate ; caudal filament usually very thick at its base, 

 tapering to a fine point at its distal end, about equal in length to the 

 body ; anterior flagellum finer and longer than the caudal filament ; con- 

 tractile vesicles two or three in number, located near the anterior extremity ; 

 endoplast subcentral. Length of body 1-930". 



HAB. Fresh water and infusions. 



The animalcule according with the above diagnosis and accompanying 

 illustrations, while referred by Stein * to the Cercomonas crassicauda of Dujardin, 

 appears scarcely to conform with the animalcule upon which this title was originally 

 conferred. The species as described by the last-named writer is said to correspond 

 closely in general appearance with Monas lens, and is regarded as a probable 

 transient phase of that type. It is further spoken of as attaching itself at 

 will by its posterior extremity, which then becomes drawn out in a tail-like 

 manner, and is again absorbed into the substance of the parenchyma on its 

 resumption of a free-swimming state. It is evident that we have here a form 

 closely related to one of the several species of the newly-introduced genus Oikomonas, 

 and an animalcule, so far as it is possible to decide in the absence of any explanatory 

 text, entirely distinct from the Cercomonas crassicauda of Friedrich Stein. In several 

 of the examples figured by this last authority, lobate or more or less attenuate 

 pseudopodal prolongations are, as shown at PI. XIV. Fig. 16, protruded from around 

 the base of the caudal filament, representing probably the amoeboid phase preceding 

 encystment or genetic union. 



Cercomonas globulus, Duj. 



Body subglobose, somewhat pointed anteriorly, surface slightly tuber- 

 cular ; flagellum and posterior filament subequal in length, two or three 

 times as long as the body, the former more slender and undulating, the 

 latter stiff. Length of body 1-2000". HAB. Marsh water. 



Cercomonas fusiformis, Duj. 



Body fusiform, inflated centrally, tapering at the two extremities ; 

 flagellum and posterior filament long and slender. Length of body 

 1-1700". HAB. Infusions of moss. 



Cercomonas cylindrica, Duj. PL. XIV. FIG. 21. 



Body elongate-cylindrical, about four times as long as broad, tapering 

 posteriorly, surface smooth ; flagellum and posterior filament slender, 

 equalling the body in length. Length of body 1-2500". 



HAB. Infusions of moss. 



* ' Infusionsthiere,' Abth. iii., 1878. 



