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 taken the sacramentum to another. The name imperator was not borne by this assistant to the throne unless it was specially conferred, as it was by Vespasian on Titus and by Hadrian on Antoninus Pius. It is uncertain whether the possessor of the tribunicia potestas and of the proconsulare imperium in its lower form had to have these powers reconferred on his accession to the throne. In the case of the imperium, since it fell short of that required for the imperial position, reconferment is probable. But yet the possession of such a power seemed to create a continuity in the Principate, and the state seemed never to have lost its head.

A second mode of nomination was effected by the Princeps designating his intended successor as his heir. It was not merely that this was an effective way of showing one's will, but it actually pointed to a transmission of the crown property (patrimonium) which accompanied the Principate. Gaius attempted to employ this mode of designation in favour of his sister Drusilla, and Tiberius showed either that he had left the succession open, or that he contemplated a joint Augustate, by making his great-nephew Gaius and his grandson Tiberius Gemellus joint heirs.

Adoption was as effective a means of emphasising one's intentions. Such an adoption by the Princeps might be by testament, but it need not follow the legal forms, and required only a public announcement through a contio whether in the Forum, the Senate, or the camp. It was thus that Galba named Piso as his successor, but adoption usually accompanied the gift of quasi-imperial power, as in the cases of Tiberius, Trajan, Antoninus Pius, and Marcus Aurelius.

We have already noticed the method by which the Princeps, sometimes with the help of the Senate, could announce his wishes as to the succession by the gift of the name of Caesar. This