 Although much of the assembly's authority was usurped by the emperors, membership in a tribe remained an important part of Roman citizenship, so that the name of the tribe came to be incorporated into a citizen's full nomenclature.The number of tribes varied over time; tradition ascribed the institution of thirty tribes to Servius Tullius, the sixth King of Rome, but ten of these were destroyed at the beginning of the Republic.Several tribes were added between 387 and 241 BC, as large swaths of Italy came under Roman control, bringing the total number of tribes to thirty-five; except for a brief experiment at the end of the Social War in 88 BC, this number remained fixed.