506 PROTOZOOLOGY 



(p. 29) living in the heliozoans as symbionts. 



The Heliozoa multiply by binary fission or budding. Incomplete 

 division may result in the formation of colonies, as in Rhaphidi- 

 ophrys. In Actinosphaerium, nuclear phenomena have been studied 

 by several investigators (p. 204). In Acanthocystis and Oxnerella 

 (Fig. 59), the central granule behaves somewhat like the centriole 

 in a metazoan mitosis. Budding has been known in numerous species. 

 In Acanthocystis the nucleus undergoes amitosis several times, thus 

 forming several nuclei, one of which remains in place while the other 

 migrates toward the body surface. Each peripheral nucleus becomes 

 surrounded by a protruding cytoplasmic body which becomes cov- 

 ered by spicules and which is set free in the water as a bud. These 

 small individuals are supposed to grow into larger forms, the central 

 granules being produced from the nucleus during the growth. For- 

 mation of swarmers is known in a few genera and sexual reproduc- 

 tion occurs in some forms. The Heliozoa live chiefly in fresh water, 

 although some inhabit the sea. Taxonomy and morphology (Penard, 

 1905, 1905a; Cash and Wailes, 1921; Roskin, 1929, Valkanov, 1940). 



Without gelatinuous envelope 

 Without flagella 



Pseudopodia arise from thick basal parts, branching 



Family 1 Actinocomidae 



Pseudopodia not branching, cytoplasm highly vacuolated 



Family 2 Actinophryidae (p. 507) 



With 1-2 flagella Family 3 Ciliophryidae (p. 508) 



With gelatinous envelope; with or without skeleton 

 Without flagella 



Without chitinous capsule 



Without definite skeleton Family 4 Lithocollidae (p. 508) 



With chitinous or siliceous spicules or scales 



With chitinous spicules. . . .Family 5 Heterophryidae (p. 510) 

 With siliceous skeleton 



Cup-like plates over body; 2-3 pseudopodia often grouped 



Family 6 Clathrellidae (p. 511) 



Scales flattened, not cup-like 



Family 7 Acanthocystidae (p. 511) 



With chitinous retiform capsule Family 8 Clathulinidae (p. 513) 



With numerous flagella, among axo podia; siliceous scales 



Family 9 Myriophryidae (p. 514) 



Family 1 Actinocomidae Poche 



Genus Actinocoma Penard. Body spherical; one or more contrac- 

 tile vacuoles; nucleus with a thick membrane, central; filopodia, not 

 axo podia, simple or in brush-like groups; fresh water. 



A. ramosa P. (Fig. 214, a). Average diameter 14-26ju. 



