Section 66. In a town which has not authorized the election of a road commissioner or commissioners or a surveyor or surveyors of highways, or which, having a road commissioner or commissioners or a surveyor or surveyors of highways, has voted in accordance with section twenty-one that a superintendent of streets be appointed by the selectmen, the selectmen shall, as soon after the annual town meeting as may be, appoint in writing a superintendent of streets, who shall receive such compensation as the selectmen or the town determine and shall be removable by them when the public interest requires. He shall be sworn to the faithful performance of his duties, and shall hold office until the next annual town meeting or until his successor is qualified. Upon the qualification of a superintendent of streets appointed by the selectmen in accordance with a vote under said section twenty-one, the office or offices of highway surveyor or surveyors or road commissioner or commissioners shall terminate.