 In "Last of the Time Lords", when the Master is fatally wounded, he chooses not to regenerate, essentially committing suicide rather than regenerate and be kept prisoner by the Doctor forever.This again implies that regeneration is not inevitable and can indeed be refused.Upon encountering the remains of fellow Time Lord the Corsair in "The Doctor's Wife", the Doctor refers to the Corsair as both male and female, hinting that Time Lords can switch genders upon their regenerations; this is confirmed in "Dark Water", in which the Master, previously seen in various male incarnations for over forty years,<ref name="terror of the autons"></ref> returned as a female.<ref name="dark water"></ref> The Thirteenth Doctor also regenerated as a woman in "The Woman Who Fell to Earth".