The election of members was by co-optation on the motion of the president, who, with a flamen, was himself elected for one year.
All the members were patricians, vacancies being filled by co-optation from young men whose parents were both living; membership was for life, subject to certain exceptions.
Nevertheless, the seven great companies continued to choose the magistrates by co-optation among themselves.
The conseil general fell more and more into the background, the members of the other councils gradually obtained the privilege of being irremovable, and the system of co-optation resulted in the creation of a close monopoly of political offices in the hands of a few leading families.
When the tenure of the religious colleges - formerly filled up by co-optation - was submitted to popular election, a change effected by a lex Domitia of 104 B.C., a new type of comitia was devised for this purpose.