The physiological theory associated with this belief has already been touched on. The spirit-child is laid by the bringer on the woman's head. Blood from her body rushes there, and on this tide of blood the baby gradually descends until it settles in the womb. The blood helps to build the body of the child—it nourishes it. That is the reason why, when a woman becomes pregnant, her menstruous flow stops. A woman will see that her menstruation has stopped. She will wait one, two, three moons, and then she will know for certain that she is pregnant. A much less authoritative belief maintains that the baby, is inserted per vaginam.
Another version of the story of reincarnation ascribes more initiative to the pre-incarnated infant. It is supposed to be able to float of its own will towards the Trobriands. There it remains, probably in company with others, drifting about the shores of the island, awaiting its chance to enter the body of a woman while she bathes. Certain observances kept by girls in coastal villages are evidence that the belief has vitality. The spirit children are imagined, as around Tuma, to be attached to drift logs, scum, leaves, and branches, or else to the small stones on the bottom of the sea. Whenever, through wind and tide, much debris accumulates near the shore, the girls will not enter the water for fear they might conceive. Again, in the villages on the northern coast, there is a custom of filling a wooden baler with water from the sea which is then left overnight in the hut of a woman who wishes to conceive, on the chance that a spirit-child might have been caught in the baler and transfer itself
