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



stigma, parietal chromatophore and one pyrenoid ; asexual re- 

 production by repeated division of all the cells, each cell thus 

 forming a new colony ; sexual reproduction unknown. Only 

 one species. 



P. CAUDATA Kofoid, 1899, p. 419, PL XXXVIII. Colony 

 of horse-shoe-shape outline, twisted about one-eighth of a turn 

 from right to left; maximum size 165X145X25/1; posterior 

 end with 3 or 5 prolongations, or tails, from the common sheath ; 

 cells 16 or 32, arranged in a marginal row of 10 or 12, and a 

 central area of 6 or 20; oblate sphaeroidal, 15-20X15-18 ^. 

 Figs. 19 and 20. 



In fresh water, 111. 



The alternating position of the cells, the cilia from one pro- 

 jecting on the opposite side of the colony from the cilia of the 

 next cell, seems to indicate an originally rounded colony, com- 

 pressed so that the cells from opposite sides have been pushed 

 in between each other. This, with the peculiar twist to 

 the membrane, strongly separates this plant from all hitherto 

 known forms. It is noteworthy that the twist of the plane is in 

 the direction corresponding with the most frequent direction of 

 revolution for the species. 



5. EUDORINA Ehrenberg, 1832, p. 78. 



Colonies globose or ovoid, usually composed of 16-32-64 cells ; 

 cells distributed nearly uniformly through the peripheral por- 

 tion of the hyaline, gelatinous mass, globose or subglobose, 

 with thin membrane, red stigma, and one or more pyrenoids ; 

 externally produced into a hyaline pointed projection with two 

 cilia, projecting from the surface of the colony. Asexual 

 reproduction by successive division of cells, ultimately forming 

 colonies like the parent ; sexual reproduction by oogonia and 

 antheridia borne by separate individuals ; all the vegetative 

 cells being transformed into antheridia, or into oogonia ; 64 

 fusiform or pyrifortu antherozoids, with two cilia, formed in 

 each antheridium ; ripe oospores brownish, with smooth ex- 

 ternal membrane, developing into new colonies. Onhy one 

 species. 



E. ELEGANS Ehrenberg, 1832, p. 78, PI. II, fig. 10 ; Phyk. 

 Univ., No. 231 ; E. stagnate Wolle, 1887, p. 160, PI. CLII, figs. 

 11-23. Colonies 50-200 /a diam. ; usually of 32 cells, arranged 

 in three parallel circles of 8 each, with 4 at each pole ; cells 

 12-24 )" diam. Fig. 21. In standing water, Pa., 111., Wash. 



Europe, So. America, New Zealand. 



