132 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



1. G. SOCIALE (Dujard.) Warming, 1876, p. 82; Oltmanns, 

 1904, p. 150, fig. 95, 2 ; G. tetras Wittr. and Nordst., Alg. 

 Exsicc., No. 50. Colony 4-celled, 20-48 /j. wide, vegetative 

 cells oval, 9-20 X 5-14 M, often with two indentations in the 

 outer end, cruciately arranged about a central, quadrangular, 

 open space. N. H., Mass. Europe. 



2. G. PECTORALE Miiller, 1773, p. 60; Wolle, 1887, p. 163, 

 PI. CLI, figs. 15-18; Phyk. Univ., No. 287. Colony 25-90^ 

 wide, composed of 16 cells, 4 central and 3 at each side; cells 

 5-15 yu. diam.; akinetes spherical, 12-15 M diam., producing 4 

 biciliate cells, each of which develops to the normal colony. 

 Fig. 16. Me., Mass., Conn., N. J., Pa., N. Y., Ont., 111., Cal. 



Europe, Asia, Africa. 



In the fully developed i6-cell colony, there is a quadrangular 

 space between the four central cells, and 16 triangular spaces 

 among the surrounding cells ; at the four-celled stage of devel- 

 opment this species is distinguished from G. soiiale by having 

 two triangular spaces, while G. sotiale has a quadrangular cen- 

 tral opening. 



2. PANDORINA Bory, 1824, p. 600. 



Colony globose or subglobose, 8, 16, 32 or 64 cells forming 

 a botryoidal mass, surrounded by a wide, gelatinous coating ; 

 cells with close, thin membrane, red stigma, and two cilia ; 

 chromatophore with one pyrenoid. Asexual reproduction by 

 continued division of the cells ; sexual reproduction by the union 

 of similar biciliate gametes, produced singly in any cell of the 

 colony ; by the union of two such gametes, of the same or dif- 

 ferent size, a zygote is produced, of reddish color, which after a 

 period of rest produces 1-3 large, biciliate red zoospores ; these 

 after a period of rest produce new colonies by vegetative divi- 

 sion. 



P. MORUM (Mull.) Bory, 1824, p. 600; Ehrenberg, 1838, 

 p. 53, PI. II, fig. 33 ; Wolle, 1887, p. 161, PI. CUII, figs, i-io ; 

 P. B.-A., No. 1175. Colony globose to ellipsoid, up to 220 /u, 

 broad, usually of 16 cells, rarely more or less; cells 9-15 /u, 

 diam.; zygote with smooth external membrane. Fig. 17. Mass., 

 Wis., 111., Cal. Europe, Asia, So. America, New Zealand. 



3. PLEODORINA Shaw, 1894, p. 279. 



Colony spherical or ellipsoid, containing biciliate cells 

 arranged in a single layer near the surface of the colony ; cells 

 of two kinds, vegetative cells in the anterior part of the colony, 

 gonidial cells in the posterior part ; cells unconnected, each with 



