...Flatworms are what are known as obligate endoparasites. They live inside of the host entering the body through ingestion of larvae or eggs. They are not creatures that go around attacking people.
Mulder, this is amazing! [looking at the flukeman] its vestigial features seem parasitic, but it has primate physiology. Where the hell did it come from?
Somebody shoved this under my door. I guess you really do have a friend in the FBI. And, Mulder, when you see Skinner to hand in field report, I hope that you know that I'd consider it more than a professional loss if you decided to leave.