In geophysics the refraction or reflection of seismic waves is used for research into the structure of the Earth's interior, and man-made vibrations are often generated to investigate shallow, subsurface structures.
Flatworms are considered acoelomate, since they have no body cavity, and roundworms are pseudocoelomate because they have a body cavity, but it is not derived from the splittiâ¦ng of the mesoderm tissue. Also, flatworms only have one opening in their digestive system unlike roundworms with two.
Best Answer: Platyhelminthes consists of flat worms. They are dorsoventrally flattened. Have a gastrovascular cavity or no digestive system. No segments. Example) Planerian Nematoda is an unsegmented pseudocoelomate. No circulatory system. Consists of Roundworms. Annelia consists of segmented worms.