Completely convective models have been constructed for stars of masses 009, 008, 007, 006, 005, and 0 04 (solar units),taking into account the non-relativistic degeneracy of the stellar material. It is shown that there is a lower limit to the mass of a main-sequence star. The stars with mass less than this limit \)ecome completely degenerate stars or "black" dwarfs as a consequence of gravitational contracti9n, and, therefore, they never go through the normal stellar evolution.