Solution:
The neural system of annelids (e.g., Pheretima) consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
Physalia (a cnidarian) has a network of neurons.
Pisaster is a starfish. Its neural system consists of a nerve ring and five radial nerves extending into the arms.
Chordates (e.g., Petromyzon) possess a single dorsal nerve cord.
