228 PROTOZOOLOGY 



2000-3000 cells; 8-24 macrogametes; zygotes 30-50/i in diameter, 

 with reticulate ridges on shell. Partheno genetic colonies up to 400/x; 

 1500-3000 cells; 8 or 10 gonidia, 40-60ju in diameter; young colonies 

 100-200/i in diameter. North America. 



V. perglohator P. Dioecious. Male colonies 300-450^; 5000-10,000 

 cells, with delicate cytoplasmic connections; 60-80 microgameto- 

 cytes. Female colonies 300-550/x; 9000-13,000 cells; 50-120 macro- 

 gametes; zygotes 30-34)Lt, covered with bluntly pointed spines. 

 Parthenogenetic colonies up to 1.1 mm; 3-9 gonidia; young colonies 

 250-275M. North America. 



Genus Gonium Miiller. 4 or 16 individuals arranged in one plane; 

 cell ovoid or slightly polygonal; with 2 flagella arranged in the plane 

 of coenobium; with or without a gelatinous envelope; protoplasmic 

 connections among individuals occur occasionally; asexual reproduc- 

 tion through simultaneous divisions of component cells; sexual re- 

 production isogamy; zygotes reddish; fresh water. 



G. socials (Dujardin) (Fig. 99, c). 4 individuals form a discoid 

 colony; cells 10-22^ by 6-16ai wide; in open waters of ponds and 

 lakes. 



G. pedorale M. (Fig. 99, d). 16 (rarel}^ 4 or 8) individuals form a 

 colony; 4 cells in center; 12 peripheral, closely arranged; cells 5-14/^ 

 by lOyu; colony up to 90/x in diameter; fresh water. 



G. formosum Pascher (Fig. 99, e) 16 cells in a colony further 

 apart; peripheral gelatinous envelope reduced; cells similar in size 

 to those of G. sociale but colony somewhat larger; freshwater lakes. 



Genus Stephanoon Schewiakoff. Spherical or ellipsoidal colony, 

 surrounded by gelatinous envelope, and composed of 8 or 16 bi- 

 flagellate cells, arranged in 2 alternating rows on equatorial plane; 

 fresh water. 



S. askenasii S. (Fig. 100, a). 16 individuals in ellipsoidal colony; 

 cells 9/x in diameter; flagella up to 30At long; colony 78/i by 60m- 



Genus Platydorina Kofoid. 32 cells arranged in a slightly twisted 

 plane; flagella directed alternately to both sides; fresh water. 



P. caudata K. (Fig. 100, 6). Individual cells 10-15^ long; colony 

 up to 165/x long, 145/i wide, and 25)U thick; rivers and lakes. 



Genus Spondylomorum Ehrenberg. 16 cells in a compact group in 

 4 transverse rings; each with 4 flagella; asexual reproduction by 

 simultaneous division of component cells; fresh water. One species. 



S. quaternarium E. (Fig. 100, c). Cells 12-26/x by 8-15/i; colony 

 up to 60/i long. 



Genus Chlamydobotrys Korschikoff. Colony composed of 8 or 16 

 individuals; cells with 2 flagella; chromatophore ; stigma ; no 

 pyrenoid ; fresh water. 



