ZOOMASTIGINA, RHIZOMASTIGINA 335 



M. setosa (Goldschmidt) (Fig. 135, e). Up to 140m long. 



M. hylae (Frenzel) (Fig. 136, a). In the hind-gut of the tadpoles of 

 frogs and toads: 80-135^ by 21-31 m; flagellum about 10m long 

 (Becker, 1925). Development (Ivanic, 1936). 



Genus Mastigella Frenzel. Flagellum apparently not connected 

 with nucleus; pseudopods numerous, digitate; body form changes 

 actively and continuously; contractile vacuole. 



M. vitrea Goldschmidt (Fig. 135,/). 150/x long; sexual reproduction 

 (Goldschmidt). 



Genus Actinomonas Kent. Generally spheroidal, with a single 

 flagellum and radiating pseudopods; ordinarily attached to foreign 

 object with a cytoplasmic process, but swims freely by withdrawing 

 it; nucleus central; several contractile vacuoles; ho lo zoic. 



A. mirabilis K. (Fig. 136, 6). Numerous simple filopodia; about 

 10/x in diameter; flagellum 20ju long; fresh water. 



Genus Dimorpha Gruber. Ovoid or subspherical; with 2 flagella 

 and radiating axopodia, all arising from an eccentric centriole; nu- 

 cleus eccentric ; pseudopods sometimes withdrawn ; fresh water. Spe- 

 cies (Pascher, 1925). 



D. mutans G. (Fig. 136, c). 15-20;u in diameter; flagella about 20- 

 30/x long. 



Genus Tetradimorpha Hsiung. Spherical with radiating axopodia; 

 four flagella originate in a slightly depressed area; nucleus central. 

 When disturbed, all axopodia turn away from the flagellated pole 

 and are withdrawn into body, and the organism undergoes swimming 

 movement; freshwater ponds. 



T. radiata H. (Fig. 136, d, e). Body 27-38m in diameter; axopodia 

 27-65m long; flagella 38-57/z long (Hsiung, 1927). 



Genus Pteridomonas Penard. Small, heart-shaped; usually at- 

 tached with a long cytoplasmic process; from opposite pole there 

 arises a single flagellum, around which occurs a ring of extremely fine 

 filopods; nucleus central; a contractile vacuole; ho lo zoic; fresh water. 



P. pulex P. (Fig. 136,/). 6-12ju broad. 



Genus Histomonas Tyzzer. Actively amoeboid; mostly rounded, 

 sometimes elongate; a single nucleus; an extremely fine flagellum 

 arises from a blepharoplast, located close to nucleus; axostyle (?) 

 sometimes present; in domestic fowls. One species. 



H. meleagridis (Smith) {Amoeba meleagridis S.) (Fig. 137). Ac- 

 tively amoeboid organism; usually rounded; 8-21/x (average 10-14/x) 

 in the largest diameter; nucleus circular or pyriform with usually a 

 large endosome; a fine flagellum; food "vacuoles contain bacteria, 

 starch grains and erythrocytes; binary fission; during division flagel- 



