The gastrotrichs (from Greek gaster "stomach" and thrix "hair") are a phylum of microscopic animals, found in fresh water and marine environments. They are bilaterally symmetric, with a complete gut. The body is covered with cilia, especially about the mouth, and has two terminal projections that serve as adhesive tubes. Like many microscopic animals, their locomotion is primarily powered by hydrostatics, and they reproduce entirely by parthenogenesis. Originally they were thought to have a pseudocoelom, but this was an artifact created by preservation methods, and they are now known to be acoelomate. Genetic studies place them as close relatives of the flatworms. About 450 species are known. Its average life span is very short - about three days. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... Kaguya is one success from 460 attempts at growing embryos. ... A pseudocoelom is a body cavity that surrounds the tissue of the endoderm layer of the cell. ... Acoelomates consist of two modern phyla of worms -- the Platyhelminthes and Nemerteans. ... Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ...