Every commissioner appointed under section 251, before performing any duty or exercising any power by virtue of his appointment, shall take and subscribe an oath or affirmation, before a judge or clerk of one of the superior courts of the state or country in which he resides, well and faithfully to execute and perform all his official duties under the laws of this State; which oath and a description of his seal of office shall be filed in the office of the Secretary of State.
33 M.R.S. § 254