... The numerous chemoreceptors found in the skin at the anterior and in the pharynx (Grzimek 1974) are sensitive to meat juices and some species also possess rheoreceptors which are sensitive to water disturbances made by nearby prey (Meglitsch 1972). Touch receptive sense cells are located at the edges of the body and the light-sensitive eyespots (ocelli) possessed by many turbellarians, can determine the direction of a light source. At least two ocelli but often several more will be present. Turbellarians that lack ocelli respond to light via light-sensitive ectodermal cells (Grzimek 1974). Statocysts for monitoring gravity and low-frequency vibrations are found in acoels, a number of catenulids and many more highly evolved turbellarians (Grzimek 1974). They give the animal a sense of equilibrium and enable it to determine its orientation. Locomotion is essential to these animals and the outer surface of the integument consists of a single layer of epithelial ...

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