the year 1064 to the destruction of Tulan, then the statement that the Chichimec migration occurred some thirty years later must be an error. It is true that if the statements of Sahagun as to the length of the reigns of the Acolhuan and Chichimec kings be correct, the error is not nearly so considerable, but in that case the association of these kings with certain epochs of Mexican history becomes impossible. I am inclined to believe that far more reliance is to be placed on associations of this kind in tradition than upon mere numbers of years, and it is possible that some mistake may have arisen between Sahagun and his informants regarding the length of a king’s life on the one hand and the length of his reign on the other. I have therefore given premier importance to statements regarding associations in my scheme of dates. Moreover it seems far more likely from several points of view that at least a century must have intervened between the downfall of Tulan and the immigration headed by Xolotl, though there must have been a steady drift of “Chichimec” tribes southward during that period, having its commencement before the former event, to which it no doubt contributed. [Illustration: FIG. 2.--Detail from the Boturini MS., showing the commencement of the Aztec migration. From left to right: Aztlan on an island; the Aztec crossing the water; the date _1. tecpatl_; the city Colhuacan; eight other tribes, reading downwards, the Matlatzinca, Tepanec, Chichimec, Malinalca, Cuitlauaca, Xochimilca, Chalca, and Uexotzinca. (_After Seler_)] For the first half-century after their establishment at Tenochtitlan, the Aztec were ruled by a council, composed no doubt of the heads of clans; but in the year 1376 they elected a king. Nothing illustrates better the idea among the Mexicans that kingly power was inherent in certain families, than the fact that they elected Acamapitzin, whose mother was a daughter of the ruler of Colhuacan, Coxcoxtli, and therefore of Toltec descent. Simultaneously the inhabitants of Tlaltelolco elected a ruler, Quaquapitzauac, said to be connected with the ruling family of Azcapotzalco. At this time the most powerful cities in the valley were Tezcoco, whither Quinatzin had removed the Acolhuan court, which was now ruled by his successor Techotlala; Azcapotzalco, ruled by the Tepanec Tezozomoc, descended from Acolhuatzin; Coatlichan, where a member of Tzontecomatl’s family held sway; and Colhuacan, under the kingship of Coxcoxtli, of the race of Pochotl the son of Topiltzin the last Toltec king.