The appended notes, based upon the population statistics of England and Wales, fall naturally, as their title suggests, into two sections. The first consists of an attempt to identify and to measure, so far as may be possible, the more important errors introduced into the successive records through the misstatements of age to which the general population has been addicted ever since its returns were collected, and may be considered a necessary preliminary to the second, which reviews briefly the mortalityexperienced by that population, noting certain features in the changes which have occurred in the past and making some suggestions with regard to its possible course in the future.