306 PROTOZOOLOGY 



D. histadialis (Puschkarew) (Fig. 139, d-J). Similar in size; 

 but cyst with a smooth wall. 



Genus Trimastigamoeba Whitmore. Flagellate stage bears 3 

 flagella of nearly equal length; vesicular nucleus with a large 

 endosome; amoeboid stage small, less than 20;u in diameter; uni- 

 nucleate cysts with smooth wall; coprozoic. One species. 



T. pMUppinensis W. (Fig. 139. g-j). Amoeboid stage 16-18ai 

 in diameter; oval cysts 13-14^ by 8-12//; flagellate stage 16-22^ 

 by e-S/x. 



Family 2 Amoebidae Bronn 



These amoebae do not have flagellate stage and are exclusively 

 amoeboid (monophasic). They are free-living in fresh or salt wa- 

 ter, in damp soil, moss, etc., and a few parasitic; 1, 2, or many 

 nuclei; contractile vacuoles in freshwater forms; multiplication 

 by binary or multiple fission; encystment common. 



Genus Amoeba Ehrenberg (Chaos Linnaeus; Proteus M tiller; 

 Amiba Bory). Amoeboid; naked, in a few species there are indi- 

 cations that a delicate pellicle occurs; usually with a nucleus, 

 vesicular or somewhat compact; contractile vacuoles; pesudopo- 

 dia mainly lobopodia, never anastomosing with one another; 

 some students have used the nuclear structure for specific dif- 

 ferentiation, but unfortunately not always clear; holozoic; fresh, 

 brackish or salt water. Numerous species. 



A. proteus (Pallas) (Figs. 25; 32, b, c; 39,/; 41-43; 140, a, b). 

 Up to 600 fx or longer in largest diameter; creeping with a few 

 large lobopodia, showing longitudinal ridges; ectoplasm and en- 

 doplasm usually distinctly differentiated; typically uninucleate; 

 nucleus discoidal, but polymorphic; endoplasmic crystals trun- 

 cate bipyramid, up to 4.5^ long (Schaeffer); nuclear and cytoso- 

 mic divisions show a distinct correlation (p. 137); fresh water. 



A. discoides Schaeffer (Figs. 39, g; 140, c). About 400m long dur- 

 ing locomotion; a few blunt, smooth pseudopodia; crystals 

 abundant, truncate bipyramidal, about 2.5m long (Schaeffer); en- 

 doplasm with numerous coarse granules; fresh water. 



A. dubia S. (Figs. 39, h-l; 140, d). About 400/i long; numerous 

 pseudopodia flattened and with smooth surface; crystals, few, 

 large, up to 30ju long and of various forms among which at least 

 4 types are said to be distinct; contractile vacuole one or more; 

 fresh water. 



A. verrucosa Ehrenberg (Figs. 32, a, d-h; 40, a; 140, e). Ovoid 



