I kid you not...Flatworm Penis Fencing

In our lab, there is somebody who is considering using planaria to do some experiments involving motility.  These are a type of flatworm (diagram on the left) which many of you may find familiar as it is often used to practice dissecting simple organisms in an introductory biology lab/course.  

Anyways, somebody asked about planaria procreate, and after doing some searching on the web, the answer is too bizarre to be believed:  PENIS-FENCING.  That's right, according to this video, when two flatworms want to get it on, they each whip out their schlong and begin an epic duel of the penises.  Whichever gets punctured by the penis first (they are apparently rather sharp) becomes the childbearer.  This is possible as planarians are hermaphrodites, possessing both male and female sexual organs.  I highly recommend this video below, if only to marvel at the fact that the narrator says things like "it's known as penis-fencing...and the worms are the swordsmen" without cracking up, as I definitely would. 

Flatworms Penis Fencing | Movies & TV | SPIKE.com