Light (A, C) and scanning electron (B, D-I) micrographs of Arcella vulgaris. (A, B) View of several specimens to illustrate variability in shape and size of the shell. (C) View of live specimen illustrating numerous short epipodes and two typical vesicular nuclei with one large central nucleolus. (D) Apertural view to show smooth apertural surface and deeply invaginated aperture with pronounced apertural lip. (E) Dorsal view. (F, G) Lateral view showing a basal collar. (H) Close up view of aperture to show distinct apertural lip. (I) Portion of shell surface showing small organic alveoli and numerous surrounding small pores.