io6 



Aqtia tic Organism s 



ing colonies are shown within the walls of the old ones 

 in the figure. 



Often, when a weed- carpeted pond shows a tint of 

 bright transparent green in autumn, a glass of the water, 

 dipped and held to the light, will be seen to be filled 

 with these rolling emerald spheres. 



Eiiglena — Several species of this genus {fig. 30^) are 

 common inhabitants of slow streams and pools. They 

 are all most abundant in mid-summer, being apparently- 

 attuned to high tempera- 

 tures. They are common 

 constituents of the water- 

 bloom that forms on the 

 surface of slow streams. 

 Figure i (p. 15) shows such 

 a situation, where they re- 

 cur every year in June. Cer- 

 tain of them are common in 

 pools at sewer outlets, 

 where bloodworms dwell in 

 the bottom mud. When 

 abundant in such places 

 they give to the water a 

 livid green color. Their 

 great abundance makes them important agents in 

 converting the soluble stuffs of the water into food 

 for rotifers and other microscopic animals. 



Dinobryo7t — This minute, amber-tinted flagellate 

 forms colonies on so unique a plan (fig. 30/O they are 

 not readily mistaken for anything else under the sun. 

 Each individual is enclosed in an ovoid conic case or 

 lorica, open at the front where two flagella protrude 

 (fig. 30t) and many of them are united together in branch- 

 ing, a more or less tree-like colony. Since flagella 



Fig. 32. A Dinobryon colony. 



