Flatworm. Light micrograph of a Dugesia planarian flatworm. This flatworm was placed in water containing Indian ink, and the black particles have been ingested by the pharynx (yellow central area that serves as both mouth and anus), and spread throughout the intestines (black). The intestines consists of closed sacs known as diverticulae. The front (anterior) end of this flatworm is at top. Magnification: x14 when printed at 10 centimetres high.