Planaria

Planaria are members of the phylum Platyhelminthes (flatworms) in the class Turbellaria. Unlike some of the related parasites in the classes Cestoda (tapeworms) and Trematoda (flukes), planarians are largely free-living, freshwater invertebrates found in or near the sediments of ponds and streams. With triangular heads, flat worm-like bodies, and paired eyespots (ocelli) that give the appearance of being cross-eyed, the bilaterally symmetrical turbellarians are relatively easy to recognize. A piece of liver tied to a string makes a great attractant for planaria when tossed into a pond or slow-moving river.