"Bhikkhus, the descent of the embryo takes place through the union of three things. Here, there is the union of the mother and father, but the mother is not in season, and the gandhabba (consciousness of the unborn being) is not present - in this case no descent of an embryo takes place. Here, there is the union of the mother and father, and the mother is in season, but the gandhabba (consciousness) is not present - in this case too no descent of the embryo takes place. But when there is the union of the mother and father, and the mother is in season, and the gandhabba (consciousness) is present, through the union of these three things the descent of the embryo takes place.