Notes: Three strains of Hypotrichomonas acosta were isolated in axenic culture. Attempts to develop a defined medium directly from a defined medium suitable for Tetrahymena pyriformis were unsuccessful. Development of partly defined media by substitution for undefined materials in Diamond's medium were more successful. Horse serum was replaced by 1 mg. % TEM-4T (a diacetyl tartaric acid ester of monoglycerides from tallow) and 0.5 mg.% cholesterol. Yeast extract was replaced by a mixture of ribonucleotides. Inclusion of several additional components permitted reducing the Trypticase concentration from 2% to 0.25%.

Notes: SYNOPSIS. Several trichomonads from poikilotherms (Hypotrichomonas acosta, Monocercomonas colubrorum and M. sp., Trichomonas batrachorum, and Tritrichomonas augusta) grew in a nearly-defined medium to a level of 10–40% that permitted with media containing casein digests; T. augusta (4 strains) grew best. The defined medium contained TEM-4T (a semisynthetic fat based on beef-tallow fatty acids) and ascorbyl “palmitate” as sources of fatty acids. Besides ascorbyl palmitate, thiomalic and ascorbic acids, and tocopherol served as reducers and antiöxidants. High concentrations of nucleotides (adenylic, cytidylic, guanylic, and uridylic acids) seemed necessary. Indigo carmine was a useful redox indicator; the flagellates never grew in the oxidized zone. Extra trace elements and amino acids or rich natural media permitted better growth at about 34.5°C—the upper temperature limit for these trichomonads, raising the issue of a biochemical basis of a thermal barrier to the invasion of warmblooded hosts. Except for the limited carbohydrate in the nucleotides, carbohydrate could be omitted, the main substrates being a combination of glycerol, acetate, and gylcero-phosphate, posing the question of the identity of the anaerobic, presumably non-glycolytic, energy-yielding pathway.

Notes: SYNOPSIS. A polymorphic allogromiid (our strain NF) was isolated in monoxenic culture but attempts at its axenic culture failed. Growth of monoxenic cultures was stimulated by various metals and vitamins. The morphology and life cycle of this allogromiid with a prominent collar have been studied in detail. It varied in form from ovoid to elongate bioral “Shepheardella-like” forms and to irregular polyoral organisms. The organisms ranged in length from 56–385 μ (118 μ± 50.54) and in width from 35–385 μ (99 μ± 39.34). The number of nuclei per organism averaged 8.9 ± 6.3 (range 1–40). Reproduction of “Shepheardella-like” forms was by binary fission. Three types of budding have been observed and, rarely, schizogony. No evidence for sexual reproduction has thus far been seen.

Notes: Hypotrichomonas gen nov., with a feeble undulating membrane but lacking a costa, is placed in the family Monocercomonadidae Kirby of the order Trichomonadida Kirby. H. acosta (Moskowitz) from squamate reptiles is designated as the type species. It has 3 unequal anterior flagella. The proximal part of its recurrent flagellum is attached to the surface of the body along an accessory filament. A low membrane with typically a few undulations extends between the accessory filament and the body surface. The membrane, which varies greatly in length in relation to the length of the body among strains of the species, is not supported by a costa. The recurrent flagellum continues as a free posterior flagellum beyond the end of the undulating membrane and terminates in an acroneme. The capitulum of the axostyle, spatulate or scoop-shaped, is closely applied to the anteriorly located nucleus. The capitulum extends anteriorly into a crescent-shaped pelta. The relatively stout trunk of the axostyle is straight or twisted. It projects for some distance from the posterior body surface, and the terminal segment of the projecting part tapers gradually to a point. The parabasal apparatus consists of a rod- or shaped body and of a filament or filaments.In division, the full complement of flagella in each of the mastigonts is restored relatively late during division but before cytokinesis. One of the daughter individuals retains the parental undulating membrane; the other develops a new organelle. The development of the new membrane is first marked by the appearance of an acroneme, presumably recurrent flagellum, early in division. The proximal part of this flagellum becomes progressively attached to the body surface. The process of attachment is paralleled by differentiation of the accessory filament and is followed by the appearance of the undulating membrane. The parental axostyle is resorbed during division, and each daughter individual develops this organelle de wove. In the very early stages of division the parabasal consisted of two arms and in all more advanced stages of a single rod-shaped body applied to a single filament.The significance of Hypotrichonionas in the evolution of trichomonads is discussed. Its morphology and morphogenesis suggest that this genus may represent an important step in the evolution of Trichomonadidae from Monocercomonadidae.

Notes: SYNOPSIS. Two new dinoflagellates, isolated from Long Island Sound and maintained axenically, are described. Gyrodinium instriatum n. sp. changes shape and size as cultures age. Glenodinium halli n. sp. is a delicately-armored form whose plate structure differs slightly from the present diagnosis of the genus, but not sufficiently like any other genus in morphology or life history for inclusion elsewhere. In G. halli the size of the motile form and predominance of motile or vegetative stages are nutrient dependent. Both dinoflagellates illustrate the need for morphological descriptions based upon continuous culture methods in defined media.