i6o 



AQUATIC MICROSCOPY FOR BEGINNERS. 



13. PhAcus (Figs. 120, 121). 



■'The body of Phdcus is flattened, thin, and rather 

 like a small leaf. It is widest in front, usually rounded, 

 and tapering from the center to the short, pointed, 

 colorless tail-like prolongation; at the broad end it 

 has one long flagellum, often difficult to see. There 

 are in our ponds, several species, all of which are 

 green. 



1. Body not twisted at the rear, tail short, curved. Ph. 



pleuronMes, Fig. 130. 



2. Body twisted or not at the rear, tail long, straight. 



Ph. longica-Adus, Fig. 121. 



14. UvfiLLA (Fig. 122). 

 The little animals forming these rapidly swimming 

 and revolving colonies are united by their narrow ends, 

 into almost spherical microscopic masses, varying in 

 number from two or three up to forty or fifty, or even 

 more. Each Infusorium has a narrow, yellowish-green 

 band down each side of the somewhat egg-shaped 



Fig. 122. — Uv^lla. 



Fig. 123 — Tracheloc6rca^ 



body, and two long, fine flagella at the broader front 

 end. The colonies are common in early spring in 

 shallow pools with Algae. 



