10. A seat in either Chamber allotted to a single State shall remain unfilled until the Ruler of that State has acceded to the Federation, and a seat in either Chamber which is the only seat therein allotted to a group of States shall remain unfilled until the Rulers of at least one-half of those States have so acceded but, subject as hereinafter provided, so long as one-tenth of the seats in either Chamber allotted either to single States or (o groups of States remain unfilled by reason of the non-accession of a State or States, whether such non-accession be due to the minority of a Ruler or to any other cause, the persons appointed by the Rulers of States to fill seats in that Chamber may from time to time in the prescribed manner appoint persons, not exceeding one-half of the number of seats so unfilled to be additional members of that Chamber:
Provided that the right to appoint such additional members shall not be exercised after the expiration of twenty years from the establishment of the Federation.
A person appointed under this paragraph as an additional member of either Chamber shall be appointed to fill his seat for a period of one year only.