164 



FRESH-WATER BIOLOGY 



214 (215, 216) 



PlanUoncma resembles in many respects the form described by Wittrock as Binuclearia but 

 Schmidle makes it a new genus. The two genera should be made the subject for further in- 

 vestigation. 



_______ — 7TJrv-svT357s — jTOi„_ Fig. 219. Planklonema Imler- 



n7^^a^P^<r^^l)L>:SQZD^!'^T^-^ Urnii Schmidle. X about 1000. 



^ — Q -'. ^' - S ^^V-J Z. (After Schmidle.) 



212 (199, 211, 213) Chromatophore a parietal network. Microspora Lagerheim. 

 Chromatophores band- like or netted and thickened at intervals; 



membrane often becoming fragmented into H-shaped pieces. Repro- 

 duction by macrozoospores and microzoospores. 



Filaments free, unbranched; sometimes resembling Conferva. Mem- 



FiG 220 Microspora trane thick, somewhat gelatmous, and distinctly made up of H-shaped 



omaem Lagerheim. pieces, the ends of the H either just meeting or overlapping. Reproduc- 



X 34s. (After West.) tion by macrozoospores with four cilia, and microzoospores with two ciUa. 



213 (igg, 211, 212) Chromatophores many, parietal, disc-shaped. Filaments 

 fine, unbranched, rarely (Aeronemum) branched. Repro- 

 duction by mono-cihate zoospores 214 



Filaments unbranched, at first attached: no pjrrenoids. 



Tribonema Derbes and Solier. 



Filaments light green, soft to the touch. Length of cells one to several times the 

 breadth, sometimes shghtly swollen at the middle. Chromatophores from two to many, small, 



parietal. Reproduction by zoospores, one or two of 

 which are formed in a cell and hberated by the 

 membrane falhng into H-shaped pieces. Zoospores 

 obovate, asymmetrical, with two chromatophores in 

 the anterior part, one cihum, and no pigment spot. 

 Resting cells may occur. 



Structure of cells and zoospores as in Tribonema; filaments 

 composed of segments of 4 to 8 cells; each formed from the 

 contents of a single vegetative cell, the ruptured wall of 

 which is visible at the end of the segment. Division rarely 



longitudinal. . . Bumilleria Borzi. 



Filaments usually short. Zoospores the same as in Tribonema, but liberated through a dis- 

 solved portion of the membrane, instead of through a circular spHt dividing the membrane into 

 two portions. Resting cells may be formed. 



Fig. 222. Bumilleria 

 sicula Borzi. X about 

 330. (After Borzi.) 



Fig. 221. Tribonema minor Klebs. 

 X 800. (Original.) 



2IS (214, 216) 





216 (214, 215) 



Structure of cells and zoospores as in Tribonema. Filaments 

 minute, richly branched, easily passing into a unicellular 

 condition Aeronemum Snow. 



Chromatophores pale, sev- 

 eral in a cell, without pyrenoids 

 and closely applied to the mem- 

 brane. Reproduction by zoo- 

 spores whidi have a single dli- 

 um, a small chromatophore, and 

 a pigment spot. They move 

 with an amoeboid motion. This 

 may be the same as Moiiocilia 

 Gemeck, though the branching 

 is much more abundant than 

 is described in that form. 



Fig. 223. Aeronemum polymor- 

 phum Snow. X 225. (Original.) 



