Do worms have brains?

The cerebral ganglion serves as a worm's brain. It is a collection of neurons, nerves and supporting structures that process input from the outside world, such as heat, light, movement and moisture. The ventral nerve on the underside of a worm is primarily responsible for sensory input.

The marine ragworm has a brain with many similarities to the human brain. In particular, the ragworm displays evidence of learning behavior, which is codified by the presence of a cerebral cortex. In humans, the cortex governs all aspects of consciousness, from memory to learning. Marine biologists have traced the human-worm connection to a shared ancestry that diverged 600 million years ago.