Yet at a later time these men were explained to be representatives, not of Osiris, but of his enemy Typhon,(219) and the killing of them was regarded as an act of vengeance inflicted on the enemy of the god. Similarly, the red oxen sacrificed by the Egyptians were said to be sacrificed on the ground of their resemblance to Typhon;(220) though it is more likely that originally they were slain on the ground of their resemblance to the corn-spirit Osiris. We have seen that the ox is a common representative of the corn-spirit and is slain as such on the harvest-field. Osiris was regularly identified with the bull Apis of Memphis and the bull Mnevis of Heliopolis.(221) But it is hard to say whether these bulls were embodiments of him as the corn-spirit, as the red oxen appear to have been, or whether they were not rather entirely distinct deities which got fused with Osiris by syncretism. The fact that these two bulls were worshipped by _all_ the Egyptians,(222) seems to put them on a different footing from the ordinary sacred animals whose cults were purely local. Hence, if the latter were evolved from totems, as they probably were, some other origin would have to be found for the worship of Apis and Mnevis. If these bulls were not originally embodiments of the corn-god Osiris, they may possibly be descendants of the sacred cattle worshipped by a pastoral people.(223) If this were so, ancient Egypt would exhibit a stratification of the three great types of religion corresponding to the three great stages of society. Totemism or (roughly speaking) the worship of wild animals—the religion of society in the hunting stage—would be represented by the worship of the local sacred animals; the worship of cattle—the religion of society in the pastoral stage—would be represented by the cults of Apis and Mnevis; and the worship of cultivated plants, especially of corn—the religion of society in the agricultural stage—would be represented by the worship of Osiris and Isis. The Egyptian reverence for cows, which were never killed,(224) might belong either to the second or third of these stages. The fact that cows were regarded as sacred to, that is, as embodiments of Isis, who was represented with cow’s horns, would indicate that they, like the red oxen, were embodiments of the corn-spirit. However, this identification of Isis with the cow, like that of Osiris with the bulls Apis and Mnevis, may be only an effect of syncretism. But whatever the original relation of Apis to Osiris may have been, there is one fact about the former which ought not to be passed over in a chapter dealing with the custom of killing the god. Although the bull Apis was worshipped as a god with much pomp and profound reverence, he was not suffered to live beyond a certain length of time which was prescribed by the sacred books, and on the expiry of which he was drowned in a holy spring.(225) The limit, according to Plutarch, was twenty-five years;(226)