Every chairman of a committee of the House of Representatives or of the Senate who is ex officio a member of any commission or board shall continue to be a member of such commission or board after each general election and until his successor shall be appointed chairman of such committee of the House or Senate and, if a vacancy occurs in any such chairmanship or the chairman is unable to serve by reason of temporary disability or other cause when the General Assembly is not in session, the Speaker of the House or the President of the Senate shall designate some member of such committee of the House or Senate, as the case may be, to serve as such member of the commission or board in the place of such chairman until the next meeting of the General Assembly or until the temporary disability is removed.