Traces of the doctrine in its early phase, prior to its formal adoption in Greece, appear in the story of Alcmaeon. Thucydides,[85] in his account of the islands known as the Echinades, in western Greece, which were gradually, owing to the silting up of the river Achelous, becoming part of the mainland, mentions the following legend: ‘when Alcmaeon, son of Amphiaraus, was wandering over the earth after the murder of his mother, he was told by Apollo that here he should find a home, the oracle intimating that he would never find deliverance from his terrors until he discovered some country which was not yet in existence and not seen by the Sun at the time when he slew his mother; there he might settle, but the rest of the earth was accursed to him. He knew not what to do till at last, as the story goes, he espied the deposit of earth made by the Achelous, and he thought that a place sufficient to support life must have accumulated in the long time during which he had been wandering since his mother’s death.’ This conception of pollution is very Semitic, and reminds us of the Biblical allusion to Cain[86] as ‘cursed from the face of the earth,’ but it is also to a certain extent Greek, since there was not in historical Greece any purgation for wilful matricide or, if we may trust Plato,[87] for wilful kin-slaying. In the Apolline era Greek kin-slaying was punished, according to Plato,[87] by death, and it was so punished in a later Israelite penal code. In the Pelasgian era, kin-slayers, condemned to perpetual exile, were often compelled to wander for years and years. Their wandering must have been almost proverbial, yet its meaning was understood. But the picture of a kin-slayer wandering till he finds an unpolluted piece of earth can only be attributed to the fanciful interpretation of a novel religious law which as yet was not fully comprehended. We have already discussed[88] Miss Harrison’s views in regard to Bellerophon and the ‘plain of wandering.’ Apollodorus tells us[89] that Bellerophon was purified by Proetus. Miss Harrison says[90] ‘in those old days he could not be purified.’ We agree that he could not be purged in Homeric times, because the rite was unknown: if in later times he was said to have been purged, it became necessary to suppose that the crime which he committed was involuntary. But Homer says nothing of Bellerophon’s kin-slaying.[91] It was probably an invention of later minds intended to explain the Homeric reference to the ‘Aleïan plain’ which was interpreted as ‘the plain of wandering,’ after the analogy of the ‘wandering’ in the legend of Alcmaeon.