But while the more ancient tribal forms had thus undergone a process of change and modification similar to that which characterised the Irish tribe, and left merely its shadow behind it in the geographical district and the function of the _Toshachdoracht_, it is in the reign of David the First that the sept or clan first appears as a distinct and prominent feature in the social organisation of the Gaelic population, and owing to the light thrown upon the ancient state of the earldom of Buchan as a Celtic _Mortuath_ by the Book of Deer only. During the period of the _Mormaers_ of Buchan prior to Garnait and Colban, who were _Mormaers_ or earls in the reign of David, we find the _Toisechs_ mentioned generally as concurring in grants of land; but in the time of these two _Mormaers_ a grant of land is made by Comgill mac Caennaig, _Tosech_ of Clan Canan; and Colban, _Mormaer_ of Buchan, and Eva, daughter of Garnait his wife, and Donnachach mac Sithig, _Toisech_ of Clan Morgan, mortmained all the previous offerings to God, Drostan, Columcille, and Peter, that is, to the monastery of Deer, and this grant is witnessed, among others, by the two sons of the _Toisech_. The _Toisech_ of the _Tuath_ had thus by this time acquired a sufficient _Deis_ to form a sept of his kin and dependants, of which he now appears as the head, but the clans in this district only show themselves to disappear at once before the advancing colonisation of the eastern districts by a Teutonic population. [Sidenote: Clan Macduff and its privileges.]