RHIZOPODA. 5 



Order 4. Amceboidea. Shape-changing Rhizopods with a contractile 

 vacuole. Movement and reception of food effected by means of blunt 

 pseudopodia. Sometimes a skeleton. Reproduction usually by binary 

 fission, sometimes by gemmation. Resting-cysts (hypnocysts) common 

 Amoeba, Lithamoeba, Hyalodiscus, Plakopus, Pelomyxa, Difflugia 

 with membranous shell strengthened by foreign particles, Arcella with 

 shagreen-like shell. 



Order 5. Foraminifera (Reticularia). Rhizopods with an amoeba -like 

 body, emitting filiform pseudopodia which branch and anastomose. Pos- 

 sess a (usually calcareous) shell. 



A. Imperforata. Shell with a single or a sieve-like opening ; 

 (more rarely two or a few openings). Gromia, one-chambered. Milio- 

 lina, many-chambered. 



B. Perforata. Shell with pores. Lagena. Orbulina ; Globi- 

 gerina. Polystomella; Nummulina. Eozobn, a doubtful form from 

 the Precambrian (Laurentian). 



