Diagram of a Radiata
In the Radiata, the starfish manifests one of the simplest forms of nervous systems. it consists of a central mass, with five arms radiating from it. In the center is the mouth, and beneath it the stomach or gastric cavity, which sends branches to each limb. The nervous system consists of five similar ganglions situated in the central portion at the base of the arms. These ganglions are connected and each sends off nerve-filaments to corresponding limbs.