Cytochemical studies using 1-(4-chloromercuriphenylazo)-naphthol-2 (Mercury Orange), a specific reagent for the detection of sulfhydryl groups, were carried out on the giant multi-nucleated amoeba, Pelomyxa carolinensis. Distribution of -SH groups was compared in normal well-fed organisms, starved amoebas and in sodium arsenite-treated individuals. The hypothesis that spindle fibre formation during mitosis involves, in part, oxidation of -SH groups to -SS- bonds and that peripheral nuclear granules play a role in spindle fibre formation was investigated. Preliminary investigations on mouse and toad muscle fibres were carried out for the purpose of confirming Bennett's results as well as to test the specificity of Bennett's Mercury Orange technique for -SH. Considerable time was spent in observing the living amoeba. Included in these observations was feeding behaviour, reaction to various stimuli and reproduction. Prior to the -SH studies, the general morphology of P. carolinensis was investigated in considerable detail using various fixation and staining techniques. Likewise, mitosis in this amoeba was thoroughly studied. Synchronous division of the many nuclei (as observed by Kudo and Schaeffer) was confirmed. Relationship of the amoeba's contour to the stage of nuclear division was studied. This relationship proved helpful in the study of -SH groups in the dividing nucleus since it provided a means of choosing a specifically desired mitotic stage. / Science, Faculty of / Zoology, Department of / Graduate