Mention briefly about the circulatory system of earthworm

Explanation

Hearts in Pheretima : The dorsal blood vessel and the ventral blood vessel are connected by a pair of pulsatile hearts, in each of the seventh, ninth, twelth and thirteenth segments. Of these four pairs, the anterior two pairs connect only the dorsal blood vessel to the ventral.blood vessel. Hence they are called lateral hearts. The posterior two pairs connect both the dorsal blood vessel and the supraoesophageal blood vessel with the ventral blood vessel. Hence, they are called lateral oesophageal hearts. These two types of hearts also differ in the number and arrangement of their valves. Four pairs of valves are present in each lateral heart, while three pairs of valves are present in each lateral oesophageal hearts. Hearts.allow the blood to flow into the ventral blood vessel only.