The nervous system of the earthworm does not contain a brain.

The nervous system of the earthworm is relatively simple compared to that of more complex organisms. It consists of a series of interconnected ganglia, nerve cords, and a nerve ring. However, it lacks a well-defined brain.

Nerve Ring:
The earthworm's nervous system begins with a nerve ring, which is a circular structure located around the pharynx. The nerve ring serves as a central control center for coordinating the activities of the worm's body.

Nerve Cord:
From the nerve ring, two nerve cords extend longitudinally along the body of the earthworm. These nerve cords run parallel to each other along the ventral side of the body. The nerve cords are connected by smaller nerves, which branch off to innervate specific regions of the body.

Ganglia:
At regular intervals along the nerve cords, there are clusters of nerve cell bodies called ganglia. Ganglia act as local integration centers and are responsible for processing sensory information and generating appropriate motor responses. Each ganglion is connected to its neighboring ganglia, allowing for communication and coordination between different parts of the worm's body.

Brain:
Unlike more complex organisms, such as humans, the earthworm does not possess a highly developed brain. A brain is a centralized control center that receives and processes sensory information, initiates motor responses, and performs complex cognitive functions. While the nerve ring in the earthworm serves as a rudimentary brain-like structure, it does not possess the same level of complexity or functionality as a true brain.

In conclusion, the nervous system of the earthworm includes a nerve ring, nerve cords, and ganglia, but it lacks a well-defined brain. The nerve ring serves as a central control center, while the nerve cords and ganglia are responsible for coordinating the activities of different parts of the worm's body.