Flatworm. Light micrograph of a planarian flatworm (Dugesia lugubris). The front (anterior) end, which is at top, includes a pair of eyes (black spots surrounded by a clear area). The black markings are internal structures called diverticulae, and comprise the flatworm's intestines. The rectangular area approximately mid-way down the flatworm's body is the structure that serves as both the mouth and anus. The bump near the bottom of the mouth/anus is the penis. Magnification: x14 when printed at 10 centimetres high.