somewhat flattened on the side against the substrate; wall thin, 

 firm, smooth, composed of 1 piece, the cytoplasm highly reticulate 

 and vacuolate in older cells; chromatophores 1 (in younger cells) 

 to numerous disc-like or ovate plates, distributed parietally in the 

 cytoplasm; uninucleate at first, becoming multinucleate before the 

 formation of amoeboid, rhizopodal swarmspores; contractile vac- 

 uoles, oil bodies, leucosin, and usually a red pigment-spot present. 



Perone dimorpha Pascher 1932b, p. 685 

 PL 95, Figs. 25, 26 

 Cells 13-60/x in diameter; amoeboid swarmers 7-15fi in diameter. 

 On mosses in an acid bog pond. Mich. 



PLEUROG ASTER Pascher 1939, p. 469 



Cells solitary, or incidentally clustered in 2's and 4's, fusiform, 

 ellipsoid, or irregularly lunate, sometimes transversely flattened; 

 wall smooth, thickened at the poles and extended into short and 

 blunt, or long and hair-like points; chromatophores 2-4, parietal; 

 no pyrenoids; several reddish oil bodies present in the cytoplasm; 

 reproduction by autospores and biflagellate zoospores. 



Key to the Species 



Cells broadly ovate to subcylindric, or 



unsymmetrically reniform P. oocystoides 



Cells fusiform or irregularly lunate P. lunaris 



Pleurogaster lunaris Pascher 1939, p. 470 

 PI. 95, Fig. 15 

 Cells ellipsoid, fusiform, or irregularly lunate, the poles slightly 

 thickened and sometimes extended to form short knobs or horns; 

 chromatophores 2-4 parietal plates; reddish oil bodies usually pre- 

 sent in the cytoplasm; cells 8-15jU. in diameter, 12-17/x long. 

 Plankter; in Douglas Lake, Michigan. 



Pleurogaster oocystoides Prescott in Prescott, 



Silva, & Wade 1949, pp. 87, 93 



PI. 95, Figs. 19, 20 



Cells solitary, ovate, unsymmetrically reniform, or broadly elliptic, 



one side flattened or concave, the other broadly convex, the poles 



broadly rounded and furnished with a nodular thickening at one or 



both ends; chromatophores numerous parietal discs; cells 8-lOju, in 



diameter, 12-14/x long. 



[353] 



