After the demolition of the monarchy, Appius Claudius was admitted into the senate by order of the people.
Cicero testifies that, from the extinction of the monarchy, all the members of the senate were admitted by command of the people.
It is observable that the first creation of the senators was the act of the monarch; and the first patrician families claimed the sole right of admission into the senate. “Les familles qui descendoient des deux cent senateurs que “Romulus avoit créés,—se crurent seules en droit d’entrer dans le sénat.”—Mably
This right however was not granted in its utmost extent; for many of the senators in the Roman commonwealth, were taken from plebian families. For sixty years before the institution of the censorship, which was A. U. C. 311, we are not informed how vacancies in the senate were supplied. The most probable method was this; to enrol, in the list of senators, the different magistrates; viz., the consuls, prætors, the two quætors of patrician families, the five tribunes (afterwards ten) and the two ædiles of plebian families: The office of quæstor gave an immediate admission into the senate. The tribunes were admitted two years after their creation. This enrollment seems to have been a matter of course; and likewise their confirmation by the people in their comitia or assemblies.
On extraordinary occasions, when the vacancies of the senate were numerous, the consuls used to nominate some of the most respectable of the equestrian order, to be chosen by the people.
On the institution of the censorship, the censors were invested with full powers to inspect the manners of the citizens,—enrol them in their proper ranks according to their property,—make out lists of the senators and leave out the names of such as had rendered themselves unworthy of their dignity by any scandalous vices. This power they several times exercised; but the disgraced senators had an appeal to the people.
After the senate had lost half its members in the war with Hannibal, the dictator, M. Fabius Buteo, filled up the number with the magistrates, with those who had been honored with a civic crown, or others who were respectable for age and character. One hundred and seventy new members were added at once, with the approbation of the people. The vacancies occasioned by Sylla’s proscriptions amounted to three hundred, which were supplied by persons nominated by Sylla and chosen by the people.
Before the time of the Gracchi, the number of senators did not exceed three hundred. But in Sylla’s time, so far as we can collect from direct testimonies, it amounted to about five hundred. The age necessary to qualify for a seat in the senate is not exactly ascertained; but several circumstances prove it to have been about thirty years.
See Vertot, Mably, and Middleton on this subject.
In the last ages of Roman splendor, the property requisite to qualify a person for a senator, was settled by Augustus at eight hundred sestertia—more than six thousand pounds sterling.