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Diagnosis of TokophryaSuctorians whose outline may be oval, pyriform or triangular, not usually flattened laterally and only weaker so when they are. All species so far reported are freshwater. Lorica absent. Attached to invertebrates, aquatic plants or inanimate objects by means of a stalk. Tentacles arranged in 1 to 4 fascicles, usually situated on the apical surface. Actinophores, if present, simple rounded lobes and not ring-like. Reproduction by circum-invaginative endogenous budding resulting in ovoid larvae bearing 4 or 5 transverse ciliary rings. Macronucleus spherical to elongate. Key to the species of Tokophrya 1 . Tentacles in one or two fascicles Tentacles in more than two fascicles 2. All tentacles at apical end of body Most tentacles at apex but one fascicle at posterior end of body . 3. Tentacles in four fascicles on actinophores .... Tentacles in three fascicles not on actinophores. 4. Not epizooic, tentacles capitate, two contractile vacuoles . Epizooic, tentacles not capitate, one contractile vacuole . 5. Actinophores in centre of apical region surrounded by rim Actinophores at corners of apical region, not surrounded by rim 6. Tentacles in single fascicle Tentacles in two fascicles ........ 7. Single contractile vacuole, found on peritrichs .... Two contractile vacuoles, found on arthropods. 8. Tentacles long, stalk thinTentacles short but many, stalk thick 9. Ovoid body, many tentacles, stalk as long as body .Pyriform or irregular body, few tentacles, stalk half body length 10. Gregarious, grows in colonial groups Solitary 11. Junction of stalk with body simple (Fig. la) . Junction of stalk with body complex (Fig. Ib-d) T. fasciculatum . T. pyrum T. diaptomi , T. emarginata , T. quadripartita . T. manueli T. pygmaea T. okobojiensis T. carchesii T. glomerata Diagnosis of ErastophryaFreshwater or marine suctoria whose shape is pyriform, ovoid or irregularly so. Lorica and actinophores absent. Tentacles distributed all over body surface or restricted to anterior end. Posteriorly there are 2 or 3 cytoplasmic extensions that may be used as organelles of attachment. Reproduction by endogenous bud formation. Macronucleus ovoid, centrally located. Key to species of ErastophryaFreshwater, attached to peritrichs epizooic on fish, tentacles distributed all over body E. chattoni Marine, among algae, tentacles restricted to anterior half of body .. . E. odontophora family Malletiidae

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SUMMARYThe specific growth and feeding rates of Tetrahymena pyriformis GL grown axenically in proteose-peptone yeast-extract medium and monoxenically in suspensions of the bacterium Klebsiella aerogenes were studied. The relation between the initial concentration of substrate, whether bacteria or soluble organic complexes, and the maximum yield of ciliates was linear, although some inhibition was noted at higher substrate concentrations. The effective yields of Tetrahymena are 9-1 % (carbon to carbon) in axenic cultures and 50% (dry-weight bacteria to dry-weight ciliate) in monoxenic cultures. The maximum growth rates at 25" in axenic and monoxenic cultures were 0.20 and 0.22 hr-l, respectively. Carbon balance studies on axenic cultures suggested that of the carbon utilized during growth 36.5 % was incorporated into the Tetrahymena and 69 % was respired. The removal rates of K. aerogenes from suspension by T. pyriformis were studied and there was evidence which suggested that the individual feeding rate of a ciliate was governed by the concentration of ciliates as well as the concentration of bacteria present. From these observations a model for ciliate feeding was derived.

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