The commission may require every corporation or person licensed under the provisions of this act to set apart a fund, no portion of which shall be applied to the expense of such corporation or person, which shall consist of not less than ten per centum of the amount designated in each contract issued as applicable to the payment of the expenses of conducting the business of such corporation or person. Such fund shall be invested at the close of each calendar year, or oftener if the commission may require, in bonds of the character described in section four of this act,¹ and forthwith deposited with the commission, in the same manner and under the same terms as prescribed by said section, as additional security for the fulfillment of its contracts, provided such corporations² or person may deposit cash with the commission in lieu of securities.