The symmetry is bilateral in liverfluke with definite polarity of anterior and posterior ends. There is no body cavity or coelom thus the liverfluke is acoelomate. Jellyfish (Aurelia) is a coelentrate. The body symmetry is usually radial. There is no body cavity or coelom but the gastrovascular cavity or coelenteron is present. Crabs are beautifully coloured crustaceans found in both fresh water and tidal regions of sea. The body cavity is called the haemocoel. Round worms (Aschelminthes) show bilateral symmetry and the body cavity develops from the blastocoel of embryo called pseudocoel.