The persistent offender occupies, together with the juvenile offender, the central position in criminality, so that every investigation of the genesis and dynamics of his delinquency, and every elaboration of rational methods for curtailing his anti-social activities, must find a place among the fundamental tasks of modern criminology and penal policy. Hence, those provisions of the Criminal Justice Bill, 1938, which deal with the treatment of persistent offenders are undoubtedly of the greatest interest and of particular significance. They are also important because, unlike the other provisions of the Bill, they do not follow the lines set out by the course of evolution hitherto followed but absolutely break with the system established by the Prevention of Crime Act of 1908 (Part II), and they introduce one feature which is entirely new. As nearly all the modern Continental penal legislative systems have also introduced new modes of dealing with persistent offenders, an examination of the English system will be useful for comparative purposes.