PHYTOMONADINA 197 



and 4 protoplasmic projections in profile; 13-17^1 by 9-20^1; 

 fresh water. 



Genus Dysmorphococcus Takeda. Circular in front view; an- 

 terior region narrowed; posterior end broad; shell distinctly 

 flattened posteriorly, ornamented by numerous pores; sutural 

 ridge without pores; 2 fiagella; 2 contractile vacuoles; stigma, 

 pyrenoid, cup-shaped chromatophore; nucleus; multiplication by 

 binary fission; fresh water. 



D. variahilis Takeda (Fig. 92, o, p). Shell 14-19^ by 13-17/z; 

 older shells dark brown; fresh water; Maryland (Bold, 1938). 



Family 7 Volvo cidae Ehrenberg 



An interesting group of colonial flagellates; individual similar 

 to Chlamydomonadidae, with 2 equally long flagella (one in 

 Mastigophaera; 4 in Spondylomorum), green chromatophores, 

 pyrenoids, stigma, and contractile vacuoles; body covered by a 

 cellulose membrane and not plastic; colony or coenobium is dis- 

 coid or spherical; exclusively freshwater inhabitants. 



Genus Volvox Linnaeus. Often large spherical or subspherical 

 colonies, consisting of a large number of cells which are dif- 

 ferentiated into somatic and reproductive cells; somatic cells 

 numerous, embedded in gelatinous matrix, and contains a chro- 

 matophore, one or more pyrenoids, a stigma and several contrac- 

 tile vacuoles; in some species protoplasmic connections occur 

 between adjacent cells; generative cells few and large. Both 

 mono- and bi-sexual reproduction occurs; monosexual gametes 

 usually fewer and larger in size than bisexual ones, each producing 

 a young colony by repeated division; bisexual reproduction aniso- 

 gamy; zygotes usually brownish red in color, with smooth, un- 

 dulating, or spinous envelopes; fresh water. 



V. glohator L. (Fig. 93, a). Elhpsoid colony, composed of 5000- 

 20,000 cells which are 3-5yu high by up to 8/x wide; monoecious; 

 up to SOOyu in diameter; in European waters. 



V. yerglohaior Powers. Colony up to 1.5 mm. in diameter; cells 

 resemble those of V. glohator; in American waters. 



V. aureus Ehrenberg (Figs. 71; 93, h). Dioecious; cytoplasmic 

 threads relatively thin and long; cells pyriform, 5-9/^ in diameter; 

 colony 500-800/i in diameter. 



V. spermatosphaera Powers. Monoecious; cells number 1000- 

 3000; without any cytoplasmic connections; colony 150-1000/x 

 in diameter. 



