	The other theory, of which Antonio Maria Ceriani and Magistretti are the most distinguished exponents, maintains that the Ambrosian Rite has preserved the pre-Gelasian and pre-Gregorian form of the Roman Rite. Ceriani (Notitia Liturgiæ Ambrosianæ) supports his contention by many references to early writers and by comparisons of early forms of the Roman Ordinary with the Ambrosian. Both sides admit the self-evident fact that the Canon in the present Ambrosian Mass is a variety of the Roman Canon. Neither has explained satisfactorily how and when it got there. The borrowings from the Greek service books have been ably discussed by Cagin (Paléographie musicale, V), but there are Greek loans in the Roman books also, though, if Duchesne's theory of origin is correct, some of them may have travelled by way of the Milanese-Gallican Rite at the time of the Charlemagne revision. There are evident Gallicanisms in the Ambrosian Rite, but so there are in the present Roman, and the main outlines of the process by which they arrived in the latter are sufficiently certain, though the dates are not. The presence of a very definite Post-Sanctus of undoubted Hispano-Gallican form in the Ambrosian Mass of Easter Eve requires more explanation than it has received, and the whole question of provenance is further complicated by a theory, into which Ceriani does not enter, of a Roman origin of all the Latin liturgical rites: Gallican, Celtic, Mozarabic, and Ambrosian alike. There are indications in his liturgical note to the "Book of Cerne" and in "The Genius of the Roman Rite" that Mr. Edmund Bishop, who, as far as he has spoken at all, prefers the conclusions, though not so much the arguments, of Ceriani to either the arguments or conclusions of Duchesne, may eventually have something to say which will put the subject on a more solid basis.