Q.Describe the heart and circulatory system of Pheretima.

[!TLDR] Pheretima has a closed circulatory system with dorsal and ventral vessels connected by several pairs of pulsatile hearts. …

[!ANSWER] The circulatory system of Pheretima is a closed system — unlike the open, haemocoel-based system of arthropods — in which blood remains confined within a network of vessels throughout the body.

A prominent dorsal blood vessel runs the length of the body above the gut, and is the chief vessel responsible for propelling blood forward through rhythmic, wave-like (peristaltic) contractions of its own muscular walls. A ventral blood vessel runs below the gut, carrying blood in the opposite (posterior) direction and distributing it to the segmental tissues and organs. …

• Describing Pheretima's system as open (haemocoel-based) — that is the arthropod condition; annelids have a closed system. …