The Dáil Constitution (Irish: Bunreacht Dála Éireann) was the first short Irish constitution, adopted by the First Dáil in January 1919. It created a ministry or Áireacht headed by the Príomh Áire, also called President of Dáil Éireann, who was in effect the prime minister.
Because Sinn Féin had almost split between monarchists and republicans at its 1917 Árd Fhéis in order to avoid another row on the issue, no head of state was provided for in the original Dáil Éireann. The constitution was, however, amended in August 1921 at the request of the then President of Dáil Éireann, Eamon de Valera to upgrade the office to full head of state, with the office renamed President of the Republic.
Bunreacht Dála Éireann (http://sources.wikipedia.org/wiki/Bunreacht_D%C3%A1la_%C3%89ireann). Full text, in Irish, from Wikisource (http://www.wikisource.org).