At the head of each department there shall be a full-time or part-time director, appointed by the City Manager, with the approval of the Council, who shall be an administrative officer of the Municipality. He shall have supervision and control of the department subject to the direction of the City Manager. Two or more departments may be headed by the same person, and the City Manager may serve as head of one or more departments, in addition to his duties as City Manager if the Council approves.