The Serenissima Signoria were the Doge and the six Councillors of the Doge, appointed annually by the Maggior Consiglio, the closest the Republic of Venice had to an executive.
John Adams wrote about the Venetian constitution in 1787 in the “A Defense of the Constitutions of Government of the United States of America”.
The doge was the elected head of the Venetian Republic. He was elected for life by an arcane process that also included drawing lots.