In pursuance of the provisions of section 2 of the civil-service act, whenever a vacancy occurs in any position which has been or may hereafter be classified under the civil-service act, and which is not an excepted position, the filling of said vacancy, unless filled through noncompetitive examination or by reinstatement, transfer, promotion, or reduction, shall be governed as follows: 

1.  The appointing or nominating officer shall request certification to him of the names of eligibles for the position vacant, and the Commission shall certify to said officer from the proper register the three names at the head thereof which have not been three times certified to the Department or office in which the vacancy exists:  Provided, That certification for temporary appointment shall not be counted as one of the three certifications to which an eligible is entitled:  And provided further, That whenever the sex of those whose names are to be certified is fixed by any law, rule, or regulation or is specified in the request for certification the names of those of the sex so fixed or specified shall be certified, but in other cases certification shall be made without regard to sex.

2.  Of the three names certified the nominating or appointing officer shall select one, and if at the time of selection there are more vacancies than one he may select more than one name, unless otherwise directed by the Commission.

  3.  If an eligible who is not entitled to certification is certified and
  appointed, his appointment shall be immediately revoked by the
  appointing officer upon notification from the Commission.

4.  A person selected for appointment shall be notified of his selection by the appointing or nominating officer, and upon his acceptance shall receive from the appointing officer a certificate of appointment for a probationary period of six months, at the end of which period, if the conduct and capacity of the probationer are satisfactory to the appointing officer, his retention in the service shall be equivalent to his absolute appointment; but if his conduct or capacity be not satisfactory he shall be notified by the appointing officer that he will not receive absolute appointment because of such unsatisfactory conduct or want of capacity, and such notification shall discharge him from the service:  Provided, That the probation of an employee in the Indian-school service shall terminate at the end of the school year in which he is appointed:  And provided further, That the time which an employee has actually served as substitute in parts of the service where substitutes are authorized shall be counted as part of the probationary period of his regular appointment, but that time served under a temporary appointment shall not be so counted.

5.  If the appointing or nominating officer shall object to an eligible named in the