INVERTEBRATE NERVOUS SYSTEMS

A simple cnidarian An echinoderm (starfish). Not really (= coelenterate), Hydra radially symmetrical.

Starfish larvae are bilaterally symmetrical.

Image from

PLATYHELMINTHS - flatworms.

ARTHROPODS and MOLLUSCS.

APLYSIA (a sea-slug).

Dorsal and ventralnerve cords.

The phylum Chordata also includes all the vertebrates.