Negima!? Magister Negi Magi Episode 14: Frankly Speaking, in the Face of Magic, Scientific Theory Might As Well Be Nonexistent.
Episode 14 of 26 of Negima!? Magister Negi Magi, aired January 4, 2007, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Class 3-A is still stuck in the World of Illusions and now they have to figure out how to change Negi back into a human as well as find a way to get back to their own world.