Factors Which Influence the Acquisition of Flagella by the Amoeba, Naegleria Gruberi

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Abstract
1. When placed in distilled water Naegleria gruberi changes from an amoeboid organism, with little evidence of polarity, to a highly polarized free-swimming flagellate. The details of this metamorphosis are described. The change is reversible. 2. Alteration of osmotic pressure is not in itself the direct cause of the metamorphosis, though the loss of certain ions is clearly important. 3. The metamorphosis is favoured by the presence of low concentrations (less than M/80) of sodium bicarbonate, sodium lactate and sodium phosphate. 4. The flagellate form probably occurs most frequently in conditions of neutrality; but, in the presence of phosphate, acid conditions tend to be more favourable to the flagellate form, while in the presence of bicarbonate the optimum pH is nearer pH 8.0. 5. The metamorphosis to the flagellate form is suppressed by a variety of agents including lithium salts, magnesium chloride and the sulphate ion under some conditions. These all act at concentrations which leave the amoeboid form in full activity. In some cases their action is decreased by the presence of bicarbonate in the medium.