Metamorphosis and the slide of the signifier

"the first explicit reference to an 'empty signifier' of which I am aware is that of [Roland] Barthes in his essay 'Myth Today' (Barthes, 1957). 

"Whereas Saussure [a structuralist] saw the signifier and the signified... as being as inseparable as the two sides of a piece of paper, [...]  poststructuralists have rejected the apparently stable and predictable relationship embedded in this model. The French psychoanalyst Jacques Lacan wrote of 'the incessant sliding of the signified under the signifier'"  

From Daniel Chandler, Semiotics (NY: Routledge, 2002), 75