Flatworms seem to have a very curious ability.
Experiments have been done with teaching flatworms to find their way through a simple maze. The maze was constructed with light and dark coloured passages, with the light passages leading to the exit. A flatworm was taught to get through the maze by applying a small current to the flatworm whenever he chose a wrong, i.e. a dark coloured passage. After some runs, the flatworm started to get through the maze correctly.

Now comes the strange part. I don't know what led the researchers to try this, but the results are very curious indeed.

If a 'trained' flatworm was killed and its flesh was fed to a 'non-trained' one, the cannibal flatworm also ran the maze correctly.

flatworm mating rituals are bizarre. according to the hutchinson educational encyclopędia:

In many flatworm species, the sperm is not received into a genital opening, instead the penis pierces the skin to inject sperm straight into the body. As this causes some damage to the flatworm, in each sexual encounter both flatworms attempt to take the male role. Consequently flatworms will vie with each other for an hour or more with each attempting to stab the other with its penis, whilst avoiding being stabbed itself.

Flat"worm` (?), n. Zool.

Any worm belonging to the Plathelminthes; also, sometimes applied to the planarians.

 

© Webster 1913.