The nervous system in white planaria.

White planaria belongs to the class of flatworms. The way of life of flatworms gradually led to the isolation of the head section, i.e., to cephalization of the nervous system. The nervous system in planarians (as in most flatworms) consists of a head paired nerve node (“brain”), from which short brain nerves extend into the head cavities. To the posterior end of the body, two large nerve trunks branch off from the brain – the ventral and dorsal. Nerve trunks consist not only of nerve fibers, but also nerve cells, from which, in turn, lateral nerves extend to various organs and skin.