REVISION OF THE FAMILY SPIRONEMIDAE DOFLEIN (PROTISTA, HEMIMASTIGOPHORA), WITH DESCRIPTION OF 2 NEW SPECIES, SPIRONEMA-TERRICOLA N-SP AND STEREONEMA-GEISERI NG, N-SP

Two new hemimastigophoran flagellates are described using light and el ectron microscopy, and the family Spironemidae is revised. Spironema t erricola n. sp. occurs in soil from the Grand Canyon (southwest USA). It moves in a conspicuously euglenoid manner and differs from S. multi ciliatum Klebs by its vermiform shape and shorter kineties. Spironema terricola is similar to Goodey's Spironema multiciliatum from soil in England. However, Goodey's vermiform species has a very elongate nucle us and is thus neither identical with S. terricola, which has a roundi sh nucleus, nor with Klebs' lanceolate S. multiciliatum; we consider i t a new species, Spironema goodeyi n. sp. Stereonema geiseri n. g., n. sp. was discovered in the Aufwuchs (periphyton) of a river in Bavaria , Germany. The new genus differs from Spironema by its acontractility, and from Hemimastix by its shorter kineties and less plicate cortex. The fine structure of Spironema and Stereonema is very similar to that of Hemimastix Foissner et al., viz., the cortex is composed of two pl ates having diagonal symmetry and the flagellated basal bodies have as sociated a short and a long microtubular ribbon. All species have uniq ue extrusomes of the same type. The main differences between the three genera and five species recognized are contractility, length of kinet ies, body size, shape of cell and nucleus, and particulars of the cort ex and extrusomes. The phylogenetic relationships of the Hemimastigoph ora are still uncertain. However, the diagonal symmetry of the cortica l plates and the pronounced euglenoid movement of Spironema spp. sugge st a common ancestor with euglenids.