The ''circulatory wave'' (''die zirkulierende Welle'') put into eviden
ce in 1949 by Welter (Welter's vortex) in total reflection is interpre
ted as a phase defect in the scalar theory of Green and Wolf of 1953,
which is the Madelung (hydrodynamic) representation of the optical fie
ld. Some comments are added on its possible relevance for the Hamamats
u experiment aimed to clarify the wave-particle duality at the ''singl
e photon'' level of down-converted laser beams.