Rhizopoda

Rhizopoda 

a subclass of protozoans capable of forming temporary cytoplasmic protuberances, or pseudopods, which serve for movement and for capturing food (certain amoebas, as well as rhizopod gametes, form temporary flagella). The pseudo-pods may be lobate, filamentous, or radial, and they may undergo anastomosis to form nets.

The rhizopods range in size from a few microns to 3 mm (in extant species; in fossil nummulites, to 5 mm). The body consists of a transparent surface layer, or ectoplasm, and a granular inner layer, or endoplasm. The endoplasm contains a nucleus. There are five orders of Rhizopoda: (1) Amoebida, widely distributed in fresh and marine waters and in the soil (the genus Entamoeba is a parasite in the human and animal intestine); (2) Testacea, inhabitants of fresh waters; (3) Foraminifera, marine, mostly benthic (occasionally pelagic) forms with a complex life cycle that alternates sexual and asexual reproduction; (4) Heliozoa, freshwater; and (5) Radiolaria, found only in the oceans. The shells of rhizopods, which are well preserved in fossil form, are widely used in stratigraphy.

A. A. STRELKOV