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.
Important Characteristics: -. 1. They have flattened body on both sides, so they are called flatworms. They have bilaterally symmetrical body. 2. They may be free-living, for example, planaria. Some are parasites and live in the body of other animals like liver-fluke. 3.