This creature is associated with numerous stories and legends, and is imbued with symbolic meaning in alchemy.

The most common iteration of the siren is as Melusine, a creature from medieval legend. Melusine (sometimes, melusina) was, according to legend, beautiful woman with a disturbing tendency to transform into a serpent from the waist down while bathing; it is the discovery of this nature that triggers calamity. As the story is most often told, the cursed maiden is discovered in the forest by Raymond, the Duke of Aquitaine, who begs her to marry him. She agrees, on condition that he never disturb her on a Saturday, when she bathes. Raymond later grows suspicious of his young wife, and spies on her- and his shocked reaction reveals his betrayal to Melusine, who transforms herself into a dragon and departs in a shrieking fury. This story can be viewed as a metaphor for sexuality, and the contradictory duality of the female nature as viewed through medieval eyes.

The same dual-nature symbolism is also at work in alchemy, which employs the siren as a more benevolent emblem of enlightenment- the siren of the philosophers. Alchemically, the siren's two tails represent unity -of earth and water, body and soul- and the vision of Universal Mercury, the all-pervading anima mundi that calls out and makes the philosopher yearn to her.