At the annual meeting the said corporations shall elect from among the legal voters of said City a Mayor, City Clerk, four aldermen, a City Treasurer, one Constable, three listers, three auditors, and three grand jurors, who shall hold office until the next annual meeting and until their successors are duly elected and qualified, except that at the first annual meeting of said corporation two of said aldermen shall be elected for one year and two for two years; one of said listers shall be elected for one year, one for two years, and one for three years; one of said auditors shall be elected for one year, one for two years and one for three years, and at each succeeding annual election two aldermen shall be elected for two years, one lister for three years, and one auditor for three years. The City Clerk and the Treasurer shall be elected for a term of three years, and the Mayor for a term of two years.