According to a model presented elsewhere the progenitors of plane-taries are fully degenerate stars with hydrogen-rich outer shells and internal temperatures lower than those of observed white dwarfs. Apparently, these stars have gone through the white dwarf stage and evolved into invisible black dwarfs. This suggests that some among observed white dwarfs may be stars with hydrogen-rich envelopes that have still to go through the planetary stage. Tentatively, we identify these stars with light white dwarfs of DA spectra and consider possible tests of this tentative identification: