  An explicit form of charged--lepton mass matrix, predicting $ m_\tau =
1776.80 $~MeV from the experimental values of $ m_e $ and $ m_\mu$ (in good
agreement with the experimental figure $ m_\tau = 1777.05^{+0.29}_{-0.26}$
MeV), is applied to three neutrinos $\nu_e $, $\nu_\mu $, $\nu_\tau $ in order
to correlate tentatively their masses and mixing parameters. While for charged
leptons the off--diagonal mass--matrix elements turn out to be small {\it
versus} its diagonal elements, it is suggested that for neutrinos the situation
is inverse. Under such a conjecture, the neutrino masses, lepton \CKM matrix
and neutrino oscillation probabilities are calculated in the corresponding
lowest (and the next to lowest) perturbative order. Then, the nearly maximal
mixing of $\nu_\mu $ and $\nu_\tau $ is predicted in consistency with the
observed deficit of atmospheric $\nu_\mu $'s. However, the predicted deficit of
solar $\nu_e $'s is much too small to explain the observed effect, what
suggests the existence of (at least) one sort, $\nu_s $, of sterile neutrinos,
whose mixing with $\nu_e$ would be responsible for the observed deficit. In the
last Section, promising perspectives for applying the same form of mass matrix
to quarks are outlined. Two independent predictions of $|V_{ub}|/|V_{cb}| =
0.0753 \pm 0.0032 $ and unitary angle $\gamma \simeq 70^\circ $ are deduced
from the experimental values of $|V_{us}|$ and $|V_{cb}|$ (with the use of
quark masses $ m_s $, $ m_c $ and $ m_b $).
