The print gives the performers a couple of hermetic hints about the fact that this kind of canons may be performed exchanging the order of the parts. In fact, at the beginning of both parts there is a rest of three semibreves before the first clef; furthermore, the signa congruentiae appear in both parts. Hence, both the soprano and the tenor can act as antecedent, and, indeed, both versions end smoothly and consistently in F. For more information, see Bornstein, Italian Duos, vol. I, p. 131-34.