Morphology and Construction of the Shell Wall in an Agglutinate Soil Testate Amoeba Phryganella acropodia (Rhizopoda)

ABSTRACT. When grown in culture, the soil testate amoeba Phryganella acropodia constructs a shell with or without mineral grains, but of identical morphology. The availability of organic shells, from these cultures, allows for detailed examination of the formation of organic building units in the cytoplasm and their subsequent use as a network in the shell matrix. Organic building units are initially formed as spherical membrane bound vesicles at the margins of dictyosomes, but mature in the cytoplasm by incorporating additional material, some have an electron dense core. These units remain pliable until they are moulded into the shell matrix. Another series of vesicles indistinguishable during initial formation from the organic building units, when mature contain a mass of small elements. This material is discharged at the same time as the building units and is thought to be the binding cement. Inorganic chemical elements appear to be incorporated within the inner lining of the matrix and the alveoli of the organic building units; manganese being preferentially absorbed under culture conditions.