Common in the plankton of both hard and soft water lakes but 

 more frequent among dense growths of algae in shallows, especially 

 in water rich in nitrogenous matter. Mich., Wis. 



EUDORINA Ehrenberg 1832b, p. 78 



A free-swimming ovate, obovoid, or globose colony, in which 

 16-32-64 ovoid or ovate cells are inclosed within a gelatinous en- 

 velope. Cells sometimes arranged in transverse series, sometimes 

 evenly disposed throughout the colonial mucilage; 2 long flagella 

 present, which diverge widely beyond the periphery of the colonial 

 envelope; cells often with 1 or 2 anterior beaks or papillae where 

 the flagella arise; 2 minute contractile vacuoles at the base of the 

 Hagella. Chloroplast cup-shaped and parietal, with 1 to several pyre- 

 noids. Red pigment-spot laterally placed at the anterior end of the 

 cell. Cytoplasmic strands connecting the cells sometimes in evidence. 

 Anisogamous sexual reproduction by small antherozoids and bi- 

 flagellate female gametes similar in size to vegetative cells. 



Eudorina elegans Ehrenberg 1832b, p. 78 



PI. 1, Figs. 24-26 



Colony spherical or ovate with 16-32 ovoid cells evenly disposed 

 within a gelatinous envelope, or arranged in transverse series, the 

 cells usually lying near the periphery of the envelope but sometimes 

 crowded toward the interior. Cells 10-20/x, in diameter; colonies up 

 to 200/i, in diameter. 



This species shows a great deal of variation in the size and shape 

 of the colony. In liquid-preserved material the envelope shows the 

 form of £. unicocca CM. Smith, with posterior mammillate pro- 

 jections. 



Common in euplankton of hard water lakes. Mich., Wis. 



PLEODORINA Shaw 1894, p. 279 



A free-swimming globose colony of 32-128 (rarely 256) spherical 

 or ovoid cells arranged at the periphery of a gelatinous colonial in- 

 vestment. Cells differentiated and of 2 sizes, the purely vegetative 

 (toward the posterior pole) being about half the size of the repro- 

 ductive (anterior) cells. Chloroplast a parietal cup, with 1 or more 

 basal pyrenoids. Pigment-spot lateral and anterior. Flagella, 2, at- 

 tached at the anterior end of cell, just above 2 contractile vacuoles; 

 the colony swimming in a rolling or tumbling fashion. Sexual repro- 

 duction anisogamous. 



[76] 



