Here are some examples:

* Sponges: These are the simplest multicellular animals and lack any centralized nervous system. They are able to respond to stimuli, but not through a brain.

* Jellyfish: These fascinating creatures have a decentralized nervous system, with a nerve net spread throughout their bodies. While they have no brain, they can sense light, food, and danger.

* Cnidarians: This group includes jellyfish, corals, and sea anemones. Like jellyfish, they have a nerve net.

* Starfish: These are more complex than sponges and cnidarians but also lack a centralized brain. They have a ring of nerves that connects to a network of nerves throughout their arms.

* Sea anemones: These animals have a nerve net, allowing them to respond to stimuli.

* Coral: Similar to sea anemones, corals also have a nerve net.

It's important to remember: While these organisms don't have brains in the same way that humans do, they still possess complex nervous systems that allow them to interact with their environment.