As to the first, the help of magician or priest is often invoked in savage society and even in European folk-custom in case of barrenness.  Prayers, charms, potions, or food are the means used to induce conception, but perhaps at one time these were thought to cause it of themselves.  In many tales the swallowing of a seed, fruit, insect, etc., results in the birth of a hero or heroine, and it is probable that these stories embody actual belief in such a possibility.  If the stories of Conall Cernach and Aed Slane are not attenuated instances of rebirth, say, of the divinity of a well, they are examples of this belief.  The gift of fruitfulness is bestowed by Druid and saint, but in the story of Conall it is rather the swallowing of the worm than the Druid’s incantation that causes conception, and is the real motif of the tale.

Where the rebirth of a divinity occurs as the result of the swallowing of a small animal, it is evident that the god has first taken this form.  The Celt, believing in conception by swallowing some object, and in shape-shifting, combined his information, and so produced a third idea, that a god could take the form of a small animal, which, when swallowed, became his rebirth.[1205] If, as the visits of barren women to dolmens and megalithic monuments suggest, the Celts believed in the possibility of the spirit of a dead man entering a woman and being born of her or at least aiding conception,—­a belief held by other races,[1206]—­this may have given rise to myths regarding the rebirth of gods by human mothers.  At all events this latter Celtic belief is paralleled by the American Indian myths, e.g. of the Thlinkeet god Yehl who transformed himself now into a pebble, now into a blade of grass, and, being thus swallowed by women, was reborn.

In the stories of Etain and of Lud, reborn as Setanta, this idea of divine transformation and rebirth occurs.  A similar idea may underlie the tale of Fionn and Mongan.  As to the tales of Gwion and the Swineherds, the latter the servants of gods, and perhaps themselves regarded once as divinities, who in their rebirth as bulls are certainly divine animals, they present some features which require further consideration.  The previous transformations in both cases belong to the Transformation Combat formula of many Maerchen, and obviously were not part of the original form of the myths.  In all such Maerchen the antagonists are males, hence the rebirth incident could not form part of them.  In the Welsh tale of Gwion and in the corresponding Taliesin poem, the ingenious fusion of the Maerchen formula with an existing myth of rebirth must have taken place at an early date.[1207] This is also true of The Two Swineherds, but in this case, since the myth told how two gods took the form of worms and were reborn of cows, the formula had to be altered.  Both remain alive at the end of the combat, contrary to the usual formula, because both were males and both were reborn.  The fusion is skilful, because the reborn personages preserve a remembrance of their former transformations,[1208] just as Mongan knows of his former existence as Fionn.  In other cases there is no such remembrance.  Etain had forgotten her former existence, and Cuchulainn does not appear to know that he is a rebirth of Lug.