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.
Platyhelminthes, or Flatworms, are the simplest kind of worms. There are about 20,000 species in this group. They are found in many places and can be free living or parasitic. A parasite lives off of another living thing called a host and can be harmful. One of the most known flatworms is the tapeworm. Also, Flatworms are found in marine and fresh water. Type of Skeleton A flatworm has no skeleton, but has tiny bristles called cilia that help it move at least two layers of muscles under its skin. It has three cell layers called the endoderm, the mesoderm and the ectoderm. They also have the beginnings of a head region. They are a phylum of triploblastic acoelomate invertebrate animals. The word platyhelminthes comes from the Greek words 'platy' meaning flat and 'helmins' meaning worm. Their bodies are soft, unsegmented, dorsoventrally flattened with bilateral symmetry and resemble ribbons.
Platyhelminthes. The name of the phylum derives from the Greek platy meaning flat and helminth meaning worm.. The Platyhelminthes are the simplest animals that are bilaterally symmetrical and formally triploblastic (composed of three fundamental cell layers).http://www.tolweb.org/Bilateria/2459. Four Clades or Classes of Platyhelminthes: Turbellaria-The Free-Living Flatworms.omplex, through incomplete gut in free living forms, absent in some parasitic forms. The following organ systems are present. Integumentary system :The epidermis is composed of a wholly or partially ciliated, syncytial or cellular epithelium, with gland cells and sensory nerve endings.