Abstract
Flatworms are the simplest of the triploblastic, bilaterally symmetrical protos tomes. As a group , they are worm-shaped with the body usually dorso-ventrally flattened. The epidermis is ciliated. | Most members of the class Turbellaria are free- living. Although planarians have frequently been used as models of the turbellarian type, Ruebush (1940) and other authors advocate the use of Mesostoma ehrenbergii for such studies. Individuals of this species are very cosmopolitan, and have been recorded from a variety of aquatic habitats. These include saline lakes (Bayly, 1971), transitory environments such as ponds, and even puddles. In recent years, the trend has been to study these organisms from other biological aspects rather than from a purely taxonomic point of view.