2004-10-04 : If a spell is countered, it still counts as the one spell cast.

2004-10-04 : When Arcane Laboratory enters the battlefield, it will look back over the turn to see if any spell was cast before it entered the battlefield. It will notice itself being cast.

2004-10-04 : When it leaves the battlefield, the effect ends and all players are able to cast spells unrestricted again.