1 62 



Aquatic Organisms 



going in form and habit. Podoplirya will often be encoun- 

 tered by searching the backs of aquatic insects or the 

 sides of submerged twigs, or other solid support, to which 

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

 pseudopodia 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. 



^.Anthophysa; i?, Podoplirya; C, Cothurnia. 



rather thick brownish stalk. The stalk increases in 

 length and diameter w^ith 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 

 growth, 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 we have not space for their consideration here. 

 We must content ourselves with the above brief 

 mention of a few of the more common and interesting 

 free-living forms. 



