Where a district boundary line divides a lot other than by following a street, any use permitted in either district may be extended not more than 50 feet into the adjacent district, or to the boundary line of the divided lot, whichever is the lesser, by the owner or owners of the lot at the time of passage of this chapter. A use permitted in the district so extended shall thereafter be permitted only one election, after which the lot use shall be governed by the regulations of the district which has been extended.