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 



1 (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 v/hether 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 S 



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



Family Rhizomastigidae 



6 (9) FlageUum single 





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



Mastigamoeha Schultze. 

 Representative species Mastigamoeha 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. FlageUum long, very active. Nucleus small, near 

 the anterior extremity; contractile vacuole single, anterior in 

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

 vegetation. 



Fig. 362. Mastigamoeha longifilum. X looo. (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 (J. Shallow ponds in early spring. 



Fig. 363. Actinomonas vernalii. cu, contractile vacuole; n, nucleus. 

 X 600. (Alter Stokes.) 



9 (6) More than one flageUtun. 



10 



