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.
The phylum as a whole has adult bilateral symmetry and cephalization (the development of a head with sensory organs, in most members). Flatworms have three tissue layers: ectoderm, mesoderm and endoderm and a body plan that is acoelomate and sac-like with a single opening.seudocoelomate animals (such as roundworms) have a body cavity but it does not develop from splitting of the mesoderm embryonic tissue layer.Coelomate animals (humans, fish, shrimp, such as shown in Figure 4) have a body cavity lined with mesoderm cells. Figure 4.