English: The peculiarity of this cyclide is that its two reference directrices are formed by an ellipse and a straight line.

with reference to the cyclical transformation of the conics belonging to the first projection plane, it results that the locus of the centers of the generating conics is a parabola. instead the locus of the poles of the polars with respect to the same conics is an ellipse.

https://www.researchgate.net/project/Geometric-Loci/update/620d6257be8820089e0d35a3