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.
Flat worms have layers of tissues that surround their central gut. They are part of the acoelomates, and are considered hermaphroditic. Their type of cell layers are: an ectoderm, which is the outer covering, an endoderm, which is the lining of digestive spaces, and a mesoderm which is in between the other two.