In the present report we demonstrate that the spreading of Rauber’s (Koller’s) sickle material, the early primary organizer of the primitive streak and Hensen’s node (secundary organizer), also influences left/right asymmetry. Our study indicates that asymmetrically disposed Rauber’s sickle material (placed circularly in the prolongation of one of the sickle horns (mainly the left) of unincubated chicken blastoderms has, after culture, without mediation of a primitive streak or Hensen’s node, an influence on the developing asymmetry of the coelomo-cardiovascular system, by  inverting its left/right axis.