Click on this link to see Planaria in action. http://www.youtube.com/watch?v=w0QzSYQGsnA
Click on the link for a photo montage of poisonous marine flatworms of the Pacific. http://www.youtube.com/watch?v=ACqk3OqDBoA&feature=PlayList&p=E4C6B12134517B36&index=55
And of course, the flatworm everybody loves to hate, the tapeworm. http://animal.discovery.com/videos/monsters-inside-me-pork-tapeworm.html