What organs and organ systems first appear in annelids?

Ringworms have multiple organ systems. Let’s take a look at the example of an earthworm. It has a nervous system. He also has a circulatory and respiratory system. Nerve nodules and blood rings are repeated in each segment. The worm has a digestive and excretory system. If you cut the worm in half, then one of its parts will survive and recover. All because of the special arrangement of internal organs, a closed circulatory system and a very good ability to regenerate in these organisms.