The establishment of the ten new tribes led to a change in the number of the Senate. It had previously consisted of 400 members, but it was now enlarged to 500, fifty being selected from each of the ten new tribes. The Ecclesia, or formal assembly of the citizens, was now summoned at certain fixed periods; and Clisthenes transferred the government of the state, which had hitherto been in the hands of the archons, to the senate and the ecclesia. He also increased the judicial as well as the political power of the people; and enacted that all public crimes should be tried by the whole body of citizens above thirty years of age, specially convoked and sworn for the purpose. The assembly thus convened was called HELIAEA and its members HELIASTS. Clisthenes also introduced the OSTRACISM, by which an Athenian citizen might be banished without special accusation, trial, or defence for ten years, which term was subsequently reduced to five. It must be recollected that the force which a Greek government had at its disposal was very small; and that it was comparatively easy for an ambitious citizen, supported by a numerous body of partisans, to overthrow the constitution and make himself despot. The Ostracism was the means devised by Clisthenes for removing quietly from the state a powerful party leader before he could carry into execution any violent schemes for the subversion of the government. Every precaution was taken to guard this institution from abuse. The senate and the ecclesia had first to determine by a special vote whether the safety of the state required such a step to be taken. If they decided in the affirmative, a day was fixed for the voting, and each citizen wrote upon a tile or oyster-shell [OSTRACON, whence the name OSTRACISM] the name of the person whom he wished to banish. The votes were then collected, And if it was found that 6000 had been recorded against any one person, he was obliged to withdraw from the city within ten days: if the number of votes did not amount to 6000, nothing was done.