Lines on Non-degenerate Surfaces

On an affine variety $X$ defined by homogeneous polynomials, every line in the tangent cone of $X$ is a subvariety of $X$. However there are many other germs of analytic varieties which are not of cone type but contain ``lines'' passing through the origin. In this paper, we give a method to determine the existence and the ``number'' of such lines on non-degenerate surface singualrities.