The appearance of the macronucleus depends on the stage of the cell, whether the cell is in early, middle or late growth phase or is in stationary phase or whether the cell is dividing by mitosis or is undergoing meiosis. In interphase the major changes will be observed in the nucleoli as the chromatin bodies maintain a relatively constant appearance. The nucleoli often exhibit a regular beaded appearance on the surface which is seen as regularly spaced threads when the nucleolus is sectioned through its surface. Presumably these represent stages in ribosomal subunit development prior to the separation of individual subunits for transport through the nuclear pores to the cytosol. TEM taken on 1/10/73 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 16,900X. Bar = 0.25µm.