Seligmann shows that the Shilluk king was “liable to be killed with due ceremony at the first symptoms of incipient decay.” But even while he was yet in the prime of health and strength he might be attacked at any time by a rival and have to defend his crown in a combat to death. According to the common Shilluk tradition, any son of a king had a right thus to fight the king in possession, and if he succeeded in killing him he reigned in his stead. As every king had a large harem and many sons, the number of possible candidates for the throne at any time may well have been not inconsiderable, and the reigning monarch must have carried his life in his hand. But the attack on him could only take place by night with any prospect of success. Then, according to custom, his guards had to be dismissed; so the hours of darkness were of special peril. It was a point of honor for the king not to call his herdsmen to his assistance. The age at which the king was killed would seem to have been commonly between forty and fifty. The Zulus put a king to death as soon as he began to have wrinkles and gray hair. Elsewhere kings were often killed at the end of a fixed term, perhaps because it was thought unsafe to wait for the slightest symptom of decay. A unique and transformed survival of many such customs, according to Frazer, lingered in the vale of Nemi, idealized in Turner’s picture. He tells us how in ancient times and long persisting there, like a primeval rock jutting out of a well shaven lawn, the priest-king watched all night with drawn sword. He was a murderer and would himself sooner or later be slain by his successor, for this was the rule of the sanctuary. The candidate for the priesthood could only succeed to office by slaying the priest, and having slain him he retained office until he himself was slain by one stronger or craftier. Although he held the title of king, no crowned head was ever uneasier. The least relaxation of vigilance put him in jeopardy. This rule had no parallel in historic antiquity but we must go farther back. Recent studies show the essential similarity with which, with many superficial differences, the human mind elaborated its first crude philosophy of life. Hence we must study outcrops of the same institution elsewhere, and Frazer tells us that the object of his book is, by meeting these conditions, to offer a fairly probable explanation of the priesthood of Nemi. Once, only a runaway slave could break off the mistletoe from the oak, and success in this enabled him to fight the priest in single combat; if he won he would become King of the Woods.