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.
Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers. Some forms are free living but many are parasitic.Flatworms have a cephalized nervous system that consists of head ganglion, usually attached to longitudinal nerve cords that are interconnected across the body by transverse branches.onparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species. Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle. Others move along slime trails by the beating of epidermal cilia.