GENUS C YA THOMONA S. 241 



M. simplex, spindle-shaped, colourless ; motion gliding or rotatory. In water of 

 the Nile and at Berlin. 1-1720". 



M. inanis, fusiform, colourless; motion vacillating. In stagnant and foul 

 water. 1-3600". 



M sdntillans, fusiform; very active, motion vacillating. Among fresh-water 

 Confervas. 1-6000" to 1-4600". 



M. Dumalii (described by Dujardin as possessing two flagella, and therefore 

 referable to the Dimastigous group), of a deep red colour ; in vast numbers in the 

 salt-marsh water of the Mediterranean, to which they give a deep blood-colour. 



M prodigiosa, a minute red monad, producing the blood-like spots occasionally 

 appearing in bread and other farinaceous substances. (Cohn asserts this organism 

 to be a Vibrio, and not a Monas.) 



M. astasioides, Pty., of variable form, often with one or two longitudinal lines and 

 a central vacuole. 1-1340". 



M. piscatorum, irregularly oval, pointed anteriorly ; colourless ; flagellum short, 

 scarcely i^ times the length of the body; movements sluggish. 1-1400". 



M sucdssa, oval ; usually truncate, rarely pointed behind ; colourless, with large 

 vacuoles ; flagellum twice the length of the body ; movement active and revolving. 

 In fresh pond water. 1-1800". 



M, cordata, cordate as seen on one side, oval and truncate on another, rounded 

 anteriorly, hyaline or granulate; swims fast, with an oscillating motion, seldom 

 revolving ; flagellum difficult to discern, more than double the length of the body. 

 In pond water. 1-1140" to 1-1080". 



M. urceolaris, small, urceolate, obliquely emarginate in front ; colourless ; flagel- 

 lum indicated only by movement produced in the water ; motion slow. In running 

 streams. 1-2640". 



The Monas excavata of Perty, having two filaments, is not referable to this 

 present genus, and the M. rotulus, farcimen, and hilla of the same authority are 

 most probably the zoospores of Palniellaceae or higher Algae. 



GENUS II. SCYTOMONAS, Stein. 



Animalcules free-swimming, ovate, persistent in form, having a simple 

 terminal flagellum ; no distinct oral aperture. 



This genus represented by a single minute species, figured but not yet described 

 at length by Stein, differs from Monas only in its persistent shape and accompanying 

 greater rigidity of the peripheral or ectoplasmic layer. 



Scytomonas pusilla, Stein. PL. XIII. FIGS. 41 AND 42. 



Body elongate-ovate or pyriform, narrowest anteriorly, about twice as 

 long as broad ; flagellum equalling or slightly exceeding the length of the 

 body ; contractile vesicle single, situated a little in advance of the centre of 

 the body. Length 1-1600". 



HAD. Fresh water. Dividing by longitudinal fission. 



GENUS III. CYATHOMONAS, De Fromentel. 



Animalcules free-swimming, ovate or cylindrical ; abruptly truncate or 

 excavate at the anterior margin ; a single long flexible flagellum projecting 

 from the centre of this truncate area ; contractile vesicle usually conspicuous ; 

 increasing by longitudinal fission ; no distinct oral aperture. 



The genus Cyathomonas has been instituted by De Fromentel (' Microzoaires,' 

 1876) for the reception of certain flagellate types, differing from Monas only in the 



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