Taxonomic Criteria for Limax Amoebae, with Descriptions of 3 New Species of Hartmannella and 3 of Vahlkampfia

SYNOPSIS. Seven species of limax amoebae were isolated into clonal, monoxenic cultures with Aerobacter aerogenes from material collected from freshwater habitats. Studies were made of their trophic structure, nuclear division, cyst structure, some aspects of cytochemistry, and other characteristics. Six new species are described: Vahlkampfia inornata, V. avara, V. jugosa, Hartmannella limacoides, H. vermiformis, and H. exundans. The well‐known species Naegleria gruberi (Schardinger, 1899) is re‐described on the basis of 8 strains; its flagellated phase was found to be biflagellate, with rare exceptions. A correlation exists between the manner of locomotion and the pattern of nuclear division in the limax amoebae in the family Vahlkampfiidae and those in the genus Hartmannella. Trophic amoebae of all species had a PAS‐positive surface layer, altho results with H. vermiformis and H. exundans were less definite than with other species. All species except H. limacoides formed cysts in culture. The cyst walls of all cyst‐forming species were strongly PAS‐positive, but results of the zinc chloroiodide test for cellulose were negative with the method used. The genus Hartmannella Alexeieff, 1912, is re‐defined to include those species which assume a simple, monopodial limax‐like form during locomotion and have nuclear division similar to that of metazoan cells and to distinguish it from the genus Acanthamoeba Volkonsky, 1931.