The Civil Service Commission shall consist of three (3) electors of the City, not holding other municipal office or employment, to be appointed by the Mayor for a term of six (6) years each, excepting that of the members first appointed, one shall be appointed for a term of two years, one for four years, and one for six years, with the stipulation that no member is eligible to succeed themself. When a vacancy occurs during the term of any member of the Commission, it shall be filled for the unexpired term in the manner authorized for the original appointment.