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.
Animals in this phylum are acoelomate, triploblastic, bilaterally symmetrical, and unsegmented. Platyhelminths have a simple anterior brain and a simple ladder-like nervous system. Their gut has only one opening. Flatworms have NO circulatory or gas exchange systems.