From this it follows that the inhabitants of the Mexican valley received the calendar from the Maya, but, before accepting such a proposition, it will be as well to examine the calendar itself for contributory evidence. We have seen that the Zapotec calendar forms a most important link between the day-signs of the Mexican and Maya respectively, and the suggestion has been made by Seler that the Maya obtained these day-signs from the west _via_ Oaxaca, calling attention to the comparatively simple nature of the Zapotec signs, which agree in this respect with those of Mexico. The Mexican valley as the place of origin of the day-signs may be, I think, disregarded, if only for the reason that certain of the animals serving as such do not occur in that region, and the choice therefore would lie between Oaxaca on the one hand and the central Mayan region on the other. Now the difference in form between the Mexican and Zapotec signs can be explained in many cases by the fact that the Zapotec term is equivocal. That being so, it seems to me obvious that the Zapotec must have borrowed from the Maya and not _vice versa_. My argument is as follows: The Zapotec signs are simple and obvious; those of the Maya are often highly conventionalized. It would be remarkable, therefore, that the Maya should have translated the Zapotec name in the wrong sense, while it would be perfectly natural for the Zapotec to have made a mistake and to have simplified the sign in accordance with their idea of the meaning of the term. If we add to this the fact that the only two initial dates discovered in the western Maya area are, together with the Chichen date, the latest known, the conclusion seems to me inevitable that early Maya culture, enumeration, and calendar spread together from Guatemala, through Oaxaca to the Tlalhuica country (Xochicalco) and the Mexican valley, becoming attenuated in the process. The question of the development of the calendar itself is interesting. The whole system seems to show traces of several modifications and to exemplify the efforts of a primitive people to adapt their chronology to solar time. The presence of five nemontemi or uayeb days over and above the period of 360 bears the stamp of an afterthought, while the 360-day period, of eighteen months, each of which comprises a full round of the day-signs, is complete in itself and suggests that this was the original “year.” The number of the day-signs, viz. twenty, is obviously based upon the vigesimal system of counting current among these peoples, but the selection of the thirteen numerals which accompany them has not yet been satisfactorily explained. As remarked before, it is obvious that an agricultural population would soon observe that the seasons gradually became out of harmony with the year, and they must have cast about to find some check by which the discrepancy could be corrected. This check they found in the synodical revolutions of the planet Venus. We know that the Aztec