  In this study, we investigate the locus of the centers of the Meusnier
spheres. Just as focal curve is the locus of the centers of the osculating
spheres, we investigate the geometrical interpretation on the locus of the
centers of the Meusnier spheres. We proved that if the curve is a principal
line, the locus of the centers of the Meusnier spheres of the curve is an
evolute curve. Then, we give the relations between this evolute curve and the
focal curve. Also, we give some relations between helices, slant helices and
the locus of the centers of the Meusnier spheres of the curve.
