Eidolon Base Form

I was browsing some of the different summoner archetypes and one caught my eye that should put to rest any more debate about changing your eidolon's base form. The subclass Evolutionist gains the following ability:

Evolve Base Form (Su)

Starting at 8th level, whenever he gains a level, the evolutionist can change his eidolon’s base form to a new base form. Once chosen, this base form is set until the evolutionist gains another summoner level.

This ability replaces transposition.

This makes it pretty clear that a summoner can NOT change his eidolon's base form under normal circumstances.