What structural adaptations do annelids have?

http://www.scribd.com/doc/6710236/8-Parasitic-Adaptations-in-Helminths

and

http://answers.Yahoo.com/question/index?qid=20080216234909AAllzOk

hope that helps. im looking for adaptations of flatworm (Polycelis felina) that aid against water flow and came across these