FLAGELLATE PROTOZOA (MASTIGOPHORA) 



243 



glass may be supported and the protozoan, if under the proper 

 pressure, may then be rotated for study from various aspects. 



KEY TO NORTH AMERICAN FRESH-WATER MASTIGOPHORA 



I (131) Flagellated forms with animal characteristics predominating. 



Class Zoomastigophora . . 2 



Confessedly a poor definition, but no better can be given. The beginner will often be in 

 doubt whether forms under consideration are flagellated animals (Mastigophora), or flagel- 

 lated plants (unicellular algae), or less frequently flagellate stages (spores) of Protozoa and 

 Protophyta. Even authorities are not in agreement regarding the position which should be 

 assigned to specific forms; thus the Volvocina are included in both Protophyta and Protozoa 

 in this book. 



2(118) Without protoplasmic collars. . . Subclass Lissoflagellata . . 3 



3 (36) Very plastic, often producing pseudopodia. Order Monadida . . 4 



4 (15) Not forming colonies and without lorica c 



5 (12) Pseudopodia present; flagella, one or two. 



Family Rhizomastigidae 



6 (9) Flagellum single 



7 (8) Pseudopodia lobe-like or pointed, sometimes branched. 



Mastigamoeba Schultze. 

 Representative species Mastigamoeba longifilum Stokes 1886. 



Body very changeable in shape, often producing distinct 

 pseudopodia; movements usually slow, repent, but sometimes 

 the animal glides forward rapidly without pseudopodia being 

 formed. Flagellum long, very active. Nucleus small, near 

 the anterior extremity; contractile vacuole single, anterior in 

 position. Length 12 to 30 /i. Standing water, among decaying 

 vegetation. 



Fig. 362. Mastigamoeba longifilum. x 1000. (After Conn.) 



8 (7) Pseudopodia ray-like, often capitate Actinomonas Kent. 



Representative species Actinomonas vernalis Stokes 1885. 



Body subspherical, changeable in shape, free swimming or 

 temporarily attached by a short stalk. Pseudopodia few, radi- 

 ating from any part of the periphery, simple or branched. 

 Nucleus subcentral; contractile vacuoles several. Diameter 

 about 20 n. Shallow ponds in early spring. 



Fig. 363. 



Actinomonas vernalit. cv, contractile vacuole; n, nucleus. 

 X 600. (After Stokes.) 



More than one flagellum 10 



