Flatworms are flattened, leaf-like forms living in damp places on land, in freshwater streams of ponds, or along the seacoast while a variety of other species are parasitic. Some of the parasitic species attain the great length of six to thirteen meters (20 to 40 feet). This parasitic flatworm diagram shows the (m) mouth, the (o) opening of the reproductive system, and (s) sucker and spines for attachment. The digestive system is stippled and the nervous system is black.
Winchell, Alexander Sketches of Creation (New York, NY: Harper & Brothers, 1870)