FIG. 28.1 Simple multicellularity. Cells in simple multicellular organisms show little differentiation and remain in close contact with the external environment. Many groups of eukaryotic organisms display simple multicellularity: (a) Uroglena, a stramenopile alga found commonly in lakes; (b) Epistylis, a stalked ciliate protozoan that lives attached to the surfaces of fish and crabs; and (c) Prasiola, a bladelike green alga only a single cell thick, found on tree trunks and rock surfaces.