236 ORDER FLAGELLATA-PANTOSTOMATA. 



the group, pass through a repent phase of existence, its correspondence under such 

 conditions with the members of the Rhizo-flagellate genus Mastigamceba of Max 

 Schulze must be eminently conspicuous. 



Monas obesa, Stein, sp. PL. XIII. FIGS. 20 AND 21. 



Body elongate, subcylindrical, widest and rounded posteriorly, attenuate 

 and conically pointed anteriorly, about three times as long as broad, 

 the periphery usually produced at variable points into one or more attenu- 

 ately pointed, rectilinear, pseudopodal prolongations ; flagellum equal to or 

 exceeding the length of the body ; endoplast located in the median line 

 towards the anterior extremity ; contractile vesicle spherical, posteriorly 

 situated, sometimes divided into two secondary vesiculae ; endoplasm 

 coarsely granular. Length 1-650". HAB. Fresh water. 



This species is figured by Stein,* under the title of Cercomonas obesa; but is 

 evidently, as in the case of his Cercomonas ramulosa, correctly referable to the present 

 generic group. In addition to the two examples figured by him as possessing 

 respectively one and two posteriorly, but not terminally, developed pseudopodal 

 prolongations, a third specimen, as reproduced at Fig. 20, is represented with an 

 anterior conical prolongation only that projects close to the insertion of the fla- 

 gellum. To some extent the body-contour of this type corresponds with that of 

 Sterromonas formicina, represented at PL XXIV. Figs. 39 and 40. 



Monas irregularis, Perty. PL. XIII. FIG. 19. 



Body more or less globular, hyaline; flagellum slender throughout, 

 mostly curved at its distal extremity, over twice the length of the body ; 

 contractile vesicles two in number, minute, situated close to the lateral 

 border ; endoplast distinct, located centrally towards the anterior extremity. 

 Length 1-2500" to 1-1250". Hab. Pond water. 



The animalcule figured, and briefly alluded to by Cienkowski under the above 

 title,f is here provisionally accepted as the type of this species. The specific form 

 upon which Perty originally conferred this name, while corresponding in general 

 contour and proportions, is represented as not unfrequently exhibiting capillary or 

 angular peripheral extensions. This phase possibly represents the typical amceboid 

 condition assumed previous to the act of encystment and multiplication by segmen- 

 tation. In one of Cienkowski's figures the retention of a large particle of food 

 within a vacuole at the posterior extremity is clearly indicated. 



Monas parasitica, Cienkowski, sp. 



Body irregularly ovate, rounded anteriorly, smooth and transparent ; 

 flagellum very long and slender, more or less curved, three or four times 

 longer than the body ; contractile vesicles two or three in number, anteriorly 

 situated ; endoplast central, spherical. Length i-iooo". 



HAB. Fresh water. 



Described by Cienkowski as Pseudospora parasitica. In its normal free-swimming 

 and flagellate condition this species frequently exhibits posterior lobate extensions 

 of the periphery ; the amoeboid phase preceding encystment is of short duration. 



Infusionsthiere, 1 Abth. iii., 1878. f ' Archiv fur Mik. Anat.,' Bd. i., 1865. 



