  The current understanding of particle masses in terms of quarks and their
binding energy is not satisfactory. Both in atoms and in nuclei the organizing
principle of stability is the shell structure, while this does not seem to play
any role for particles. In order to explore the possibility that shells might
also be relevant at this inner level of aggregation, atomic and nuclear
stability are expressed by "stablines", alignments of the 1/3 power of the
total number of constituents of the most stable configurations. Could similar
patterns be found in the particle spectrum? By analyzing the distribution of
particle lifetimes as a function of mass, stability peaks are recognized for
mesons and for baryons and indeed the cube roots of their masses follow two
distinct stablines. Such alignments would be a strong indication that the
particles themselves are shell structured assuming only that each constituent
contributes a constant amount to the total mass. This is incompatible with the
prevalent view that the partons--real physical constituents seen in
deep-inelastic scattering experiments--are the quarks. The mass of the Bc
predicted by interpolation with the meson stabline is 7.4 +/-0.2 GeV. On the
baryon stabline new baryon states are predicted at 3.9 and 7.6 GeV.
