§ 418. Assignment of mortgage, lease, or other lien or charge. The holder of any mortgage, lease, or other lien or charge on registered property, in order to transfer the same or any part thereof, shall execute an assignment of the whole or any part thereof; and upon such assignment being filed in the office of the registrar, the registrar shall enter in the title book a memorial of such transfer with a reference to the assignment by its file number; he shall also note upon the instrument on file in his office intended to be transferred, and upon the registration copy thereof produced, the number of the certificate on which the memorial is entered, with the date of the entry.