The chief officers of the legion were the tribunes, and originally there was one in each legion from the three tribes--the Ramnes, Luceres, and Tities. In the time of Polybius the number in each legion was six. Their authority extended equally over the whole legion; but, to prevent confusion, it was the custom for these military tribunes to divide themselves into three sections of two, and each pair undertook the routine duties for two months out of six. They nominated the centurions, and assigned to each the company to which he belonged. These tribunes, at first, were chosen by the commander-in-chief,--by the kings and consuls; but during the palmy days of the republic, when the patrician power was preeminent, they were elected by the people, that is, the citizens. Later they were named half by the Senate and half by the consuls. No one was eligible to this great office who had not served ten years in the infantry or five in the cavalry. They were distinguished by their dress from the common soldier. Next in rank to the tribunes, who corresponded to the rank of brigadiers and colonels in our times, were the centurions, of whom there were sixty in each legion,--men who were more remarkable for calmness and sagacity than for courage and daring valor; men who would keep their posts at all hazards. It was their duty to drill the soldiers, to inspect arms, clothing, and food, to visit the sentinels, and regulate the conduct of the men. They had the power of inflicting corporal punishment. They were chosen for merit solely, until the later ages of the empire, when their posts were bought, as in the English army. These centurions were of unequal rank,--those of the Triarii before those of the Principes, and those of the Principes before those of the Hastati. The first centurion of the first maniple of the Triarii stood next in rank to the tribunes, and had a seat in the military councils, and his office was very lucrative. To his charge was intrusted the eagle of the legion. [Footnote: Liv. xxv. 5; Caes. _B.C._, vi. 6.] As the centurion could rise from the ranks, and rose by regular gradation through the different maniples of the Hastati, Principes, and Triarii, there was great inducement held out to the soldiers. In the Roman legion it would seem that there was a regular gradation of rank although there were but few distinct offices. But the gradation was not determined by length of service, but for merit alone, of which the tribunes were the sole judges. Hence the tribune of a Roman legion had more power than that of a modern colonel. As the tribunes named the centurions, so the centurions appointed their lieutenants, who were called sub-centurions. [Sidenote: Change in the organization of the legions.]