Body cavity or coelom
-:Body cavity or Coelom:- The body of Nereis is transverse section looks like a tube within a tube . The wall of the outer large tube is body wall and the wall of the inner small tube is the gut wall . In between the two walls,lies a spacious cavity called coelom or body cavity , which is filled up with afluid . The coelom is thus lined externally by parietal epithelium and internally by visceral or splanchnic epithelium . The coelom is devided into compartments by transverse partitions,called septa . The wall of each septum is perforated through which coelomic fluid communicates from one chamber to the other. Coelom of Nereis is schizocoelic and filled with coelomic fluid having amoeboid corpuscles . It act as hydrostatic skeleton and help in transportation of digested food,gasses and waste materials . -:Locomotion:- In Nereis Locomotion takes place by parapodia, musculature and coelomic fluid . Nereis shows three types of locomotion - Slow creeping :- This ty...