No contributions to the retirement system shall be made by the state, by employers, or by members prior to the commencement date, except the contribution of the state for an expense fund to pay the expenses of setting up and operating the retirement system prior to that date. On January 1, 1945, the board of trustees shall notify all employers and the employers shall notify the members that contributions will commence on that date; and thereupon this chapter with reference to such contributions will go into effect.