Five points are discussed regarding the vesicular structure isolated by fractionation techniques from the brain and liver of the guinea pig. 1. One type of vesicle, fixed by OsO(4) and shown in thin sections, is identified with the coated vesicle that has been observed in many varieties of tissues. 2. The vesicle contained in a spherical polygonal "basketwork" shown by the negative-staining techniques is identical with the coated vesicle shown in sections. 3. Despite minute observation of this basketwork we could not confirm the existence of "hairlike projections" extending from the convex cytoplasmic surface of the vesicle. We are inclined to believe, therefore, that the hairlike projections are actually the superimposed visual images of the regular hexagons and pentagons of the network composing the basketwork. 4. We repeat the hypothesis originally advanced by Roth and Porter (1) that the "coating" of the coated vesicle plays a role in the mechanism of the infolding and fission of the membrane; we suggest that these events are caused by the transformation of the regular hexagons (of the coating) into regular pentagons. 5. Finally, we make a suggestion as to the nature of those vesicles which have on their surface subparticles which look like "elementary particles (2)."