There shall be fifteen members of the Legislature, to be known as senators. Seven (7) senators shall be elected by the qualified electors of the District of St. Croix and seven (7) senators shall be elected by the qualified electors of the District of St. Thomas-St. John. One (1) senator shall be elected at large by the qualified electors of the Virgin Islands from the Virgin Islands as a whole; provided, however, that such senator shall be a person who is a bona fide resident of St. John.