in the first primitive stages the Jungian is presented as the quarrelling copulation of beasts and birds, such as hen and cock, while the later unions are represented by the copulation of human lovers, the marriage of the red man and white lady
Abraham demonstrates that alchemical copulation functions as a developmental sequence of symbolic registers, ascending from bestial to royal union, encoding the progressive refinement of the opus.
, A Dictionary of Alchemical Imagery, 1998thesis