The tenants produced by commendation were, however, hardly a class by themselves. They most likely sank into the ordinary condition of the large class of 'coloni,' &c., on the great provincial estates. And there is a passage in the 'Institutes of Justinian' which incidentally seems to imply that the ordinary 'colonus' of the later empire was very nearly in the position of the 'usufructuarius,' and held a holding which, in legal theory at least, ended with his life.[458] [p310] And if this was the generally received theory of the status of semi-servile tenants on the great estates, the probability is that the practice of single succession by regrant may have followed as a matter of convenience and as an all but universal usage. Further, if we may suppose this to have been the case on the private estates of provincial landowners, the question remains whether the semi-servile classes of tenants on the imperial domains may not have been subject to the same customary rules. «Tenants on public lands in theory 'usufructuarii.'» «Probable prevalence of the rule of single succession.» Now it must be remembered that the legal theory as regards that part of the provincial land which was not centuriated and allotted to the soldiers of the conquering Roman army as a 'colonia,' but left in the possession of the old barbarian inhabitants, was that the latter were merely usufructuary tenants, paying tribute for the use of the land which belonged now to the conquerors.[459] And although _quasi_-rights of inheritance, founded perhaps more upon barbarian usage than direct Roman law, probably grew up generally in the more settled districts of Gaul and the two Germanies, yet there may well have been grades of tenants, some with rights of inheritance and some without them. It may well be questioned whether, in the case of the 'læti' and other semi-servile tenants, hereditary rights were generally recognised. If we take into account the tendency we have noticed in the management of the provincial domains towards manorial methods and usages, it seems at least probable that the semi-servile classes of tenants under [p311] the imperial military and fiscal officers were placed much in the same position as the coloni on private villas; that, in fact, their tenure was only a usufruct for life or at will--a tenure to which, by custom, the single succession would be a natural incident. «The Romans adapted themselves to existing usages.»