(b) The terms of the members appointed prior to November 5, 1974, shall be 16 years; the terms of two appointive members to expire as heretofore on March 1st of every even-numbered calendar year, and two members shall be appointed for terms commencing on March 1, 1976, and on March 1 of each year thereafter; provided that no such appointments shall be made for terms to commence on March 1, 1979, or on March 1 of each fourth year thereafter, to the end that no appointment to the regents for a newly commencing term shall be made during the first year of any gubernatorial term of office. The terms of the members appointed for terms commencing on and after March 1, 1976, shall be 12 years. During the period of transition until the time when the appointive membership is comprised exclusively of persons serving for terms of 12 years, the total number of appointive members may exceed the numbers specified in the preceeding paragraph. In case of any vacancy, the term of office of the appointee to fill such vacancy, who shall be appointed by the Governor and approved by the Senate, a majority of the membership concurring, shall be for the balance of the term for which such vacancy exists.