The word Platyhelminthes is formed from the Greek words platy meaning flat and helminth meaning worm. Animals of this group are known as flatworms or tapeworms. The number of species in this category is about 29,487. The group Platyhelminthes was named by the scientist Gagenbaur (Gagenbaur, 1859). Some flatworms of the genus cause schistosomiasis or snail fever in humans.