Each judge of the probate division of the circuit court shall also be an ex officio circuit judge of the circuit for such additional classes of cases as may be assigned to him by the presiding judge of the circuit if he be a circuit judge and an ex officio associate circuit judge of the county for such additional classes of cases as may be assigned to him by the presiding judge of the circuit if he be an associate circuit judge. The salary payable to each such judge who serves as a judge of the probate division shall be payable to him in his capacity as such ex officio circuit judge or ex officio associate circuit judge, as the case may be, and not in his capacity as a judge of the probate division.