Section 13. Every town clerk shall, within ten days after his election and thereafter, at intervals of not more than one year, so long as he continues to hold said office, give bond to the town for the faithful performance of his duties, in a form approved by the commissioner of revenue and in such sum, not less than the amount established by said commissioner, as shall be fixed by the selectmen. If he does not give bond as herein required the selectmen may declare the office vacant and fill the vacancy in the manner prescribed in section fourteen.