How does fluid in an internal body cavity, like you saw in the round worms and the segmented worms, help with movement? Which animal phylum(a) that you studied has(ve) radial symmetry? Which animal phylum(a) that you studied has(ve) complete digestive systems? Identify the animal phylum that matches the description. complete digestive system and molts filter feeders and spicules support gastrovascular cavity and flame cells radula and muscular foot segmented with controlled movement stinging cells to stun prey