In this article we will discuss about Nereis Dumerilii:- 1. External Structures of Nereis Dumerilii 2. Body Wall of Nereis Dumerilii 3. Body Cavity or Coelom 4. Digestive System 5. Respiratory System 6. Circulatory System 7. Excretory System 8. Nervous System 9. Reproductive System. Contents: External Structures of Nereis Dumerilii Body Wall of Nereis Dumerilii Body Cavity or Coelom of Nereis Dumerilii Digestive System of Nereis Dumerilii Respiratory System of Nereis Dumerilii Circulatory System of Nereis Dumerilii Excretory System of Nereis Dumerilii Nervous System of Nereis Dumerilii Reproductive System of Nereis Dumerilii 1. External Structures of Nereis Dumerilii: The body of Nereis dumerilii is approximately 7-8 centimetres in length. The colour is light violet and the regions of the body which are richly supplied with blood vessels appear reddish. The glittering appearance of the surface is due to the intersection of two sets of fine lines. The animal is ...