Section 43. A temporary register shall be entitled to the same compensation as the register, and shall be paid by him if the appointment is caused by his absence; but if the appointment is caused by his death, removal or resignation, the temporary register shall be paid by the commonwealth. No judge or register shall receive any fee or compensation in addition to his salary for holding or attending courts or acting as judge or register in any county, nor for anything done in his official capacity, except as expressly provided by law, but any judge of probate assisting another judge in the performance of his duties may receive compensation from him, if not entitled to receive it from the commonwealth.