Any of a class of freshwater
They are sometimes considered relatives of heliozoans (organisms that for movement have extensions of {{link=cytoplasm">cytoplasm called pseudopodia, but no flagella) because of their slender, radiating pseudopodia. The cores of the pseudopodia of some helioflagellates radiate from a central granule, as they do in some heliozoans. Helioflagellate life cycles alternate between flagellate and heliozoan phases. Some members are spherical, others oval.