GENUS MONAS. 237 



The body occupies but a small space within the membranous envelope of the cyst, 

 and breaks up into numerous sporular fragments, the indigestible residue of the 

 incepted food-particles being cast aside within the cavity of the cyst 



Monas nitellarum, Cienk., sp. 



Body minute, globose ; flagellum very slender and attenuate, six or seven 

 times as long as the body ; encystment spherical, double walled. Diameter 

 1-2500". HAB. Fresh water, among decaying matter. 



Synonymous with the Pseudospora nitellarum of Cienkowski. 



Monas concava, Duj. 



Body circular, meniscoidal, concave on one side and convex on the 

 other, thin centrally, the margin tumid ; flagellum long and slender, vibrating 

 throughout its length. Diameter 1-2000". HAB. Marsh water. 



It is impossible to decide whether this and the three following species referred 

 by Dujardin * to the genus Monas, belong to that generic group as here constituted, 

 or whether they do not represent imperfectly observed or imperfectly developed 

 animalcules of other Flagellata. Their admission here must consequently be 

 regarded as entirely provisional. 



Monas elongata, Duj. 



Body elongate, nodular, flexible, and changeable in form, vacuolate ; 

 flagellum long and slender. Length 1-1250". 

 HAB. Putrid infusions with marsh water. 



Monas attenuata, Duj. 



Body ovoid, tapering at the two extremities, nodular and vacuolate ; 

 flagellum thick at its base, continuous with the pointed apical extremity. 

 Length 1-1500". HAB. Putrid marsh water. 



Dujardin intimates that a slightly more pronounced development of the posterior 

 extremity would necessitate the allotment of this form to the genus Cercomonas. 



Monas oblonga, Duj. 



Body oblong, irregular, tuberculate, enclosing numerous vacuoles ; 

 flagellum distinct, somewhat thickened at the base. Length 1-3000" to 

 1-1600". HAB. Vegetable infusions. 



Monas varians, Duj. 



Body oblong, tapering anteriorly, its substance soft and glutinous, 

 exceedingly plastic and changeable in form. Length 1-800" to 1-625". 

 HAB. Ditch water. 



Monas constricta, Duj. 



Body elongate, four or five times as long as broad, blunt, and rounded 

 posteriorly, narrower and often constricted in the centre. Length 1-1250". 

 HAB. Infusions of gelatine with chlorate of potash. 



* 'Histoire des Zoophytes Infusoires,' Paris, 1841. 



