240 ORDER FLAGELLATA-PANTOSTOMATA. 



Monas depressa, From. 



Body elongate, the two extremities rounded ; the ventral side flattened, 

 the dorsal one convex ; flagellum always directed beneath. Length 1-1600". 

 Hab. — Fresh water. 

 This is probably a species of Petalomonas. 



Monas sphserica, From. 



Body irregularly spherical ; surface granulate, enclosing minute red 

 corpuscles ; flagellum slender, about three times the length of the body ; 

 contractile vesicle conspicuous, postero-lateral. Diameter i-iooo". 



Hab. — Fresh water. 



This species is almost the only representative of the genus satisfactoril)^ deUneated 

 by De Fromentel, its larger size permitting, with the magnification of 400 diameters 

 customarily employed by him in his investigation of these minute organisms, a 

 tolerably fair appreciation of its form and structure. No details are appended 

 as to the special conditions or circumstances under which it was encountered, but it 

 would seem not altogether improbable that it represents the motile form of the 

 trimastigate type Spiundla vivipara. 



Monas ovata, From. 



Body oval, widest posteriorly ; transparent, with yellow granulations 

 towards the posterior extremity ; the anterior end pointed and hyaline ; 

 flagellum long, slender, and undulating. Length 1-2000". 



Hab. — Fresh water. 



Doubtful Species. 



The Monas crepusculum of Miiller and Ehrenberg, represented by minute 

 spherical points only, under a magnification of 800 diameters, and the M. pundum and 

 pulvisculus of the same authorities, figured in De Fromentel's recent work,* cannot be 

 admitted as independent species, being indistinguishable from the early germinating 

 conditions of numerous other larger animalcules. The following species of the 

 older writers, reproduced by Pritchard,t are in most instances too ill-defined for future 

 identification, but may be added to complete the list : — 



M. eruhcscens, Ehr., spherical, rose-coloured; motion slow and continuous; 

 diameter 1-1728". Hab. — Saltwater. 



M. enchelys, Ehr., colourless ; motion slow, continuous. In marsh water. 1-1200" 

 to 1-960". 



M. umbra, Ehr., ovate, colourless ; motion rapid. Among fresh Confervse. 

 1-2400". 



M. hyalina, ovate, colourless ; active, seems to leap or jump. In stale water. 

 1-6000" to 1-2880". 



M. gUscens, ovate, colourless ; motion gliding. In infusions of stinging-nettle. 

 1-4500". 



M. cylindrica, solitary, elongate, colourless ; motion revolving. In salt water. 

 1-1150". 



M. Okeni, elongate, red ; motion revolving, vibratory ; social. In running water. 

 1-2300". 



M. sodalis, conical, colourless; social. In water-butts. 1-700". 



* De Fromentel, 'Etudes sur les Microzoaires,' Paris, 1876. 



t ' A History of the Infusoria,' by Andrew Pritchard, 4th ed. i860. 



