The first regular session of the Legislature shall commence on the second Monday of December A.D. Eighteen hundred and Sixty Four, and the second regular session of the same shall commence on the first Monday of January A.D. Eighteen hundred and Sixty Six; and the third regular session of the Legislature shall be the first of the biennial sessions, and shall commence on the first Monday of January A.D. Eighteen hundred and Sixty Seven; and the regular sessions of the Legislature shall be held thereafter biennially.