  The new quantum number \sigma is introduced. It is shown that the
conservation of \sigma-number results in the conservation of difference between
baryon and lepton numbers obtained earlier by Georgi and Glashow. The
conservation of \sigma -number also predicts that electron type neutrino mass
is exactly zero. The quark-lepton symmetry is discussed. It is shown that the
nature of quark-lepton symmetry is reflected by the fact that elementary
particles of the same generation are subject to the symmetry transformation
represented by 4-group of diedr. It is also shown that colorless elementary
particles are subject to the same symmetry transformation. The new elementary
particles (transbaryons) are predicted.
