Mention briefly about the circulatory system of earthworm

Solution:
Earthworms (Pheretima) have closed blood vascular systems, which consists of the heart, blood vessels, and capillaries. The heart pumps blood for circulating it in one direction. Blood is supplied by smaller blood cells to the gut nerve cord and the body wall. Blood glands are present in the $4^{\text {th }}, 5^{\text {th }}$, and $6^{\text {th }}$ segments, which produce blood cells and haemoglobin dissolved in blood plasma. Blood cells in earthworms are phagocytic in nature.