Employees appointed from original appointment eligible lists and from promotional eligible lists shall be subject to a period of probation. The regular period of probation shall be six months, provided that the personnel rules may specify a longer or shorter period of probation for certain designated classes of positions, or for extension of the probation period in individual cases. However, probation may not extend beyond twelve months. The work and conduct of probationary employees shall be subject to close scrutiny and evaluation and if found to be below standards satisfactory to the appointing authority, the appointing authority may remove or demote the probationer at any time during the probationary period. Such removals or demotion shall not be subject to review or appeal. An employee shall be retained beyond the end of the probationary period and granted permanent status only if the appointing authority notifies the Personnel Director in writing that his work has been found satisfactory and that he recommends that he be given permanent status.