Alter Self for Darkvision?

[LokiDR]

Since when do you not get a Bat's Blindsight ability when Polymorphing?

You get all the natural, non-magical abilities of the form you polymorph into. While I'm sure there's lots of monsters out there that have a magical form of Blindsight... a Bat's is completely natural.

You do not get any exceptional abilities of the creature you are polymorphing into, only gross physical characteristics: physical stats, natural movement, ability to breath water. There is an arguement that constrict is a gross physical characteristic, but it definately stops before blindsight. Poly is still one of the most powerful spells in the game.

Maybe this is best way to say what abilities you can gain from alter self: if you would get it from polymorph, except where noted (stats, natural armor.)