In the legend Melusina sometimes has the tail of a fish and sometimes that of a snake; she is half human, half animal... That is the moment when the harbinger of fate, the anima, an archetype of the collective unconscious, appears.
Jung identifies Melusina as the anima appearing at a moment of catastrophic crisis, reading her half-animal form as the universal mark of the collective unconscious's intrusion into personal life.
, Alchemical Studies, 1967thesis