The other parts of the Cleisthenean constitution have to do with the organisation of the army and of the council, with a strange and novel process known as ostracism, and with local government within the demes. The military force under Pisistratus and his son had consisted of foreign mercenaries: Cleisthenes established an army of citizens. Each tribe furnished a brigade serving under the general whom the tribe had elected: at Marathon in 490 B.C. the right wing was formed by a body of troops under the Polemarch and then from right to left the ten tribal brigades were marshalled in order each under its own general[148]. [148] Herodotus VI. 111, whence the words are taken. Ar. _Const. Ath._ ch. 22. The number of the council, which Solon had fixed at four hundred, was raised by Cleisthenes to five hundred, fifty councillors being taken from each tribe[149]. In the time of the Peloponnesian war, (as will be shown further on,) the council of five hundred was a committee of citizens entrusted with the duty of controlling the proceedings of the general assembly: it considered resolutions and projects of law before they were submitted to the assembled people: the fifty councillors of each tribe enjoyed for a tenth part of the year the dignity of πρυτάνεις or presiding officers, both in the council and in the general assembly, and the name πρυτανεία was applied both to their right of presidency and to the thirty-five or thirty-six days for which they possessed it: and, as the assembly met often and had much business to attend to, such a committee was obviously necessary. The records of the age of Cleisthenes give no details about the doings of the assembly and the council: but the activity of the assembly, as we have already seen, began in that age, and it is natural to suppose that some of the later functions and organisation of the council may be referred back to this time. The opinion is confirmed by a piece of evidence from Plutarch who states incidentally that in 490 B.C. the tribe Æantis was the presiding tribe in the assembly which resolved that the Athenians should march out to resist the invader Darius[150]. It is probable that under the Cleisthenean constitution the assembly met once in each prytany. [149] Aristotle, _Constitution of Athens_, ch. 2. [150] Plutarch, Συμποσιακὰ προβλήματα I. 10.