Prytaneis
The prytaneis were the executives of the boule of Ancient Athens. They served in a prytaneion.
Origins
When Cleisthenes reorganized the Athenian government in 508/7 BCE, he replaced the old Solonian boule, or council, of 400 with a new boule of 500. The old boule consisted of 100 members of each of the four ancestral tribes. Cleisthenes created ten new tribes and made the boule consist of 50 men selected by sortition from each of these tribes.Organization
Each of the ten tribe's delegation would be an executive of the boule for one-tenth of the year rotating after, so that ten groups of prytaneis served each year. The executive officers were known as prytaneis and their term of office as a prytany. Each day, for one 24-hour period, one member of the 50 prytaneis was selected by lot to lead, serving as the chairman.Duties
The prytaneis served every day during their prytany, except during festival days. They formally called to meeting the full boule and the ecclesia of Athens. In practice many meetings were mandatory and evidence suggests that persuasive individuals could enjoin the prytaneis to call or not to call a supplementary meeting. The prytaneis received ambassadors from foreign states, held meetings decided the desirability of holding an ostracism, and generally conducted the day-to-day business of the state. They ate at public expense in the tholos, a circular edifice constructed for them next to the boule house.The selected chairman for the day administered the state seal and the keys to the state treasuries and archives. He would also serve as the head of the state, receiving and meeting with foreign envoys. This power made him in effect, the chief executive officer of Athens. No man was allowed to hold this office more than once.
During meetings of the ecclesia or boule, the current chairman also chaired these meetings. In the Fourth Century, this practice changed and the chairmanship of meetings was taken over by an office specifically created for this task the proedroi. From that point on the chairman only directed meeting of the prytaneis.