Section 7. For the purpose of protecting any species of useful fish, birds or mammals and for aiding the propagation thereof, the director may acquire in fee by purchase, gift or devise, or may lease, or with the consent of the owners, may control, any land, water or shore or the right to use the same, including the right of the public on such land or on or in such water or shore, as a wildlife sanctuary. The director, with the approval of the governor, may receive in trust for the commonwealth any grant or devise of land or any gift or bequest of personal property for the purpose of aiding in the propagation and protection of any useful fish, birds or mammals; provided, that, unless approved by the general court, no obligation shall be imposed on the commonwealth to expend in the carrying out of any trust more than the income of the trust property, or more than the income and principal thereof if by the terms of the trust the principal may be expended. Any such gift or bequest of money or securities shall be transferred forthwith to the state treasurer, who shall administer it as provided in section sixteen of chapter ten.