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.
Overview. Platyhelminthes consists of the unsegmented flatworms, which includes both free-living and parasitic species. They have bilateral symmetry, and can move by using layers of muscles, or in some species, by gliding along a slime trail using cilia.Flatworms are slightly less developed than segmented worms due to their lack of a circulatory system and complete digestive system.ome flatworms have primitive light-sensing eyes that allow them to move either towards or away from light, while other species have different types of sensors on their bodies, including chemical, balance, and water movement receptors. Most species of flatworms reproduce either sexually or asexually.