There are remarkable parallels between the rituals performed over the yam gardens by the Trobriand Islanders and those performed by the Tikopia. The strikingly similar garden rituals appear to be dramatizations, not simply of the mythic origin and structure of the gardens, but of the mythic origin and structure of society itself. The metaphor used in both cases is that of human reproduotion. Many of the differences between the two ritual systems appear to relate, in the first place, to differing theories of human reproduction and, behind them, to differing rules of descent.