Master Chymist: Assuming mutagenic form -> Standard Action ?

[Zachrid]

While an alchemist needs to drink a potion in order to mutate (it is a standard action to drink the potion), the master chymist prestige class can change (a few times a day) at will into his 'Mutagenic Form (Ex)'. However it is said that, if the player misses a will check in stressful situations, the character will 'mutate' with his next standard action:

Mutate (Su):
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A chymist may be forced to take her mutagenic form against her will by stress or damage. Anytime the character is in her normal form and has daily uses of the mutate ability available, she may be forced to switch after suffering a critical hit or failing a Fortitude save. In these situations the chymist must make a DC 25 Will save; if she fails, on her next turn she uses a standard action to change to her mutagenic form (which counts as a use of the mutate ability).
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What kind of action is needed to change to the mutagenic from, if the character wants to mutate? I.e. he isn't stressed out or he succeeded on the will check but wants to change anyway.

[Dennis Baker]

Supernatural abilities are a Standard action unless it says otherwise in the ability. (As are Spell Like Abilities)

[Zachrid]

Thank you! :)