Under the Microscope

Transfer one small planarian to a petri dish with just enough pond water to cover the worm. Using the lowest magnification objective lens (4X or 10X) follow the worm as it glides over the glass (much easier using the wide field 4X lens than the 10X). Describe the worms digestive system--which will stand out particularly clearly if your worm has recently fed.

Most species of flatworms are active carnivores. The protruding pharynx is visible, as the worm feeds on the daphnia above. The mouth is at the end of this extension. The pharynx will pin down the prey while enzymes secreted from the mouth soften the tissue. The mouth sucks in the food and digestion is completed inside the cells.