PHYTOMONADIDA 



111 



10 to 20 microns long, form a colony. In open water of ponds 

 and lakes. 



Gonium pectorale Miiller (Fig. 38, c). Sixteen individuals 

 form a colony; four individuals in the center; twelve peripheral. 

 Individuals 7 to 11 microns long. In stagnant water of ponds 

 and ditches. 



Genus Platydorina Kofoid. Cells arranged in a slightly 

 twisted plane. Flagella directed alternately to both sides. 



Fig. 38 a, b. Gonium sociale. X320 (After Fritsch). 



c. G. pectorale. X240 (After Stein). 



d. Platydorina caudata. X about 210 (After Kofoid). 



e. Spondylomorum quaternarium. X250 (After Stein). 



f. Stephanosphaera pluvialis. X190 (After Hieronymus). 

 g, h. Pandorina morum. X200 (After Pringsheim). 



h, a stage in asexual reproduction. 



Platydorina caudata Kofoid (Fig. 38, d). Found in rivers 

 and lakes. About 150 microns long by 130 microns wide. 



Genus Spondylomorum Ehrenberg. Individuals similar to 

 Carteria, but colonial. Sixteen individuals all directed an- 

 teriorly and arranged in four transverse rings. Asexual repro- 

 duction by simultaneous divisions of the component cells. 

 Sexual reproduction unknown. Fresh water. 



Spondylomorum quaternarium Ehrenberg (Fig. 38, e). About 

 45 microns long. In fresh water and soil. 



Genus Stephanosphaera Cohn. Spherical colony, with 



