22 PROTOZOA 



Suborder 1. APHROTHORACIDA. 



Naked Heliozoa with filifonn pseudopodia radiating from all sides 

 which are either with or without axial filaments; one or more nuclei 

 and contractile vacuoles present: 9 genera. 



Key to the genera of AphrotJioracida here described: 



Oj Body more or less amoeboid. 



6i Ectosarc and entosarc sharply defined ; animals appear on algae as red 

 cysts 1. Vampybella 



62 No boundary between ectosarc and entosarc 2. Nuclearia 



Ca Body not amoeboid ; form spherical. 



61 Ectosarc and entosarc not defined ; skeletal axis of pseudopodia extending to 



center 3. Actinophkys 



62 Ectosarc and entosarc sharply separated 4. Actinosph^eium 



Fig. 16 Fig. 17 Fig. 18 



Fig. 16 — Yampyrella lateritia (Leidy). Fig. 17 — Actinophrys sol (Leidy). 

 Fig. 18 — Actinosphwrium eichhorni (Leidy). 



1. Vampyrella Cienkowsky. Ectosarc hyaline; entosarc brown or 

 red, frequently vacuolated; form amoeboid, pseudopodia radiating from 

 all sides or arising from only one place: 5 species; in fresh and salt 

 water. 



V. lateritia Leidy (Fig. 16). Body spherical or elongated; diameter 

 about .06 mm. ; length of moving animals may be .24 mm. : among fresh- 

 water algae. 



2. Nuclearia Cienkowsky. Body spherical or elongate and amoe- 

 boid with homogeneous protoplasm; pseudopodia radiating from all sides 

 or arising from only one place ; one or more nuclei and many contractile 

 vacuoles: 2 species; in fresh water. 



N. simplex Cienk. Diameter about .05 mm.: among Spirogyra and 

 other fresh-water plants. 



3. Actinophrys Ehrenberg. Body spherical and not amoeboid; 

 pseudopodia radiating from all sides and with axial threads which 

 extend to center of body; ectosarc and entosarc not separate: 1 species; 

 in fresh and salt water, 



A. sol (0. F. Miiller) (Fig. 17). Diameter .05 mm.; often colonial: 

 common. 



