One segment of the assembly line used for phagosome membrane growth in P. caudatum. Cytopharyngeal ribbons bring discoidal vesicles to the left lip of the cytopharynx where the vesicles bind and then fuse with the cytopharyngeal membrane. This expands the membrane to form the phagosome. The role of the contractile cytostomal cord in this process has yet to be determined. Also brought to this area are acidosomes and carrier vesicles. Carrier vesicles contain cargo coming into the cell via parasomal sacs that is sorted from the membrane components that are to be recycled back to the plasma membrane. Sorting occurs in the early endosomes. Coated pits on the early endosomes pinch off to form the carrier vesicles. The carrier vesicles come to lie against the acidosomes where they fuse. Eventually acidosomes will fuse with the phagosome to form the phagoacidosome where the acid pH will kill the bacteria and other food organisms. TEM taken on 5/21/73 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 15,250X. Bar = 0.25µm.