Abstract
It is argued that the bi-symmetrical enhanced structures in the images of planetary nebulae - and in some H II regions - afford evidence that the outflow of matter from the central star which engenders the nebula has definitely not been isotropic. The mechanism the author suggests for the formation of such objects - the model - is the collimated outflow from a definite area on a rotating progenitor. Such an outflow will form a helix of which the projection is the observed planetary. The author has discussed the detailed velocity field of the planetary Abell 78 in confrontation with its morphology. The results show that this PN was formed by ejection from one single active region which makes a small angle with the equator of the rotating central object.
