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



outer surface covered with dome-shaped prominences with hex- 

 agonal base. Fig. 13. 



The "red snow" of arctic and high mountain regions; 



usually included in the same genus with Haematococcus pluvi- 



alis, often in the same species ; but Wille, 1903, seems to have 



determined the proper position. Greenland, Alaska. Europe. 



2. HAEMATOCOCCUS Agardh, 1828, PI. XXIV. 



Cells similar to those of Chlamydomonas but having in the 

 motile stages protoplasmic threads passing through the coating 

 from the central mass to the wall ; coating usually quite thick, 

 often different in form from the cell itself ; cell with or without 

 red stigma, often deep red in color ; asexual reproduction by 

 biciliate zoospores produced few in a cell ; probable sexual 

 reproduction by smaller biciliate gametes, produced many in a 

 cell ; but actual conjugation has not been observed. 



H. PLUVIALIS Flotow, 1844, p. 415, PI. XXIV, XXV; H. 

 lacustris, P. B.-A., No. 114; Sphaerella lacustris Hazen, 1899, 

 p. 211. Resting cells spherical, 8-80 p. diam., deep red, with 

 thick wall; dividing into 4-16 biciliate zoospores, with wide, 

 hyaline coating, through which pas's very fine, protoplasmic 

 threads ; after a short time these spores come to rest, and divide 

 like the parent cell ; this may continue for an indefinite number 

 of generations ; or at any time the cells may enter into a long 

 resting stage ; under certain circumstances the resting spore 

 may divide into 4-32 small, narrowly cylindrical or fusiform 

 spores, probably gametes. Fig. 14. Me. to Texas and Nebraska, 

 Cal. Europe. 



Common in shallow, easily dried up pools ; forming a dull 

 red coating on the bottom and any contained objects ; in the 

 active state the cells are nearly or quite green, with chroma to- 

 phore covering the cell wall, and several pyrenoids. 



3. CHLOROGONIUM Ehrenberg, 1837, p. 172, 



Cells spindle-shaped, with two cilia at the forward end ; coat- 

 ing very thin ; cells with two or more pyrenoids, a red stigma, 

 and many vacuoles. Asexual reproduction by division into 4 

 or 8 daughter cells ; sexual reproduction by zoogametes formed 

 1 6 or 32 in a cell, by successive division ; copulation taking 

 place between gametes of the same or different sizes, forming a 

 round red zygospore, at whose germination 4 new individuals 

 are produced', at first red, then green. Only one species. 



C. EUCHLORUM Ehrenberg, 1837, p. 172 ; Dangeard, 1888, 

 p. 114, PI. XI, figs. 5-13. Cells 25-35 /" l n g> 8 /u, diam., with 

 thin wall and two cilia. In quiet w^ater, aquaria, etc. Europe. 



