1 62 



Aquatic Organisms 



g< >ing in form and habit. Podophrya will often be encoun- 

 ters 1 by searching the backs of aquatic insects or the 

 sides < >f submerge d twigs, or other solid support, to which 

 it is attached. It is sessile, and reaches out its suctorial 

 pseiidopodia in search of soft -bodied organisms that are 

 its prey. 



Anthophysa is a curious sessile form that is common 

 in polluted waters. It forms very minute spherical 

 colonies that are attached to the transparent tip of a 



Fig. 73. Three sessile protozoans. 



A, Antnophysa; B, Podophrya; C, Cothurnia. 



rather thick brow r nish stalk. The stalk increases in 

 length and diameter with age, occasionally forking when 

 the colony divides. It soon becomes much more con- 

 spicuous than the colonies it carries. It often persists 

 after the animals are dead and gone. After a vigorous 

 gr< »wth, the accumulated stalks sometimes cover every 

 solid support as with a soft flocculent brownish fringe. 

 Besides these and other free-living forms, there are 

 parasitic Protozoa whose spores get into the water. 

 Some of these are pathogenic; many of them have 

 changes of host ; all of them are biologically interesting; 

 but w r e have not space for their consideration here. 

 We must content ourselves with the above brief 

 mention of a few r of the more common and interesting 

 free-living forms. 



