Who were the tribes the Lewis and Clark encountered in North Dakota? Had the Mandan and Hidatsa ever seen an African-American before? How did tribes fare in the wake of the expedition?
The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek ÏÎ»Î±ÏÏ, platy, meaning flat and á¼Î»Î¼Î¹Î½Ï (root: á¼Î»Î¼Î¹Î½Î¸-), helminth-, meaning worm) are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates.
Nervous System of Platyhelminthes. Platyhelminthes occupy a position of strategic phylogenetic importance in that they are the most primitive members of Bilateria and constitute the basal stock from which all higher animal phyla are thought to have evolved.n addition to nerve cords, well-developed nerve nets or plexuses can be found in all flatworm taxa. These include subsurface, submuscular, pharyngeal and intestinal (=stomatogastric) and reproductive nerve plexuses. In some places, the plexuses are in continuity with both main and minor nerve cords.