The deep fiber is associated with the cytopharyngeal membrane (see Smith and Bunse, Trans. Am. Microsc. Soc. 102:264-271, 1983). This membrane has acidosome-like vesicles docked at its cytosolic surface. Enlargement of this membrane tube probably permits new vacuole formation. The deep fiber is probably homologous to the postoral microtubular bundles of Paramecium. TEM taken on 2/12/71 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 11,250X. The raw negative was scanned with an Epson Perfection V750 Pro and this high resolution image is best used for quantitative analysis. Additional information available at (http://www5.pbrc.hawaii.edu/allen/).