18. Where, following the adoption of an act amending the limits of electoral districts for the following general election, the annual enumeration has been made taking into account the limits so amended, the holding of a referendum must be made in accordance with the limits as so amended and the returning-officers appointed by anticipation are competent to act as such for the purposes of the referendum; similarly, the polling-subdivisions which have been defined by anticipation are those that are to be used for the purposes of the referendum.