  The forward neutron production in the ep collisions at 300 GeV measured by H1
and ZEUS Collaborations at DESY has been used to estimate the total probability
for proton fluctuation into n pi^+ and p pi^0. The probability found is on the
order of 30%. This number is compared with the numbers obtained for the
probability of quark fluctuation into pi^+ from several alternative DIS
processes (Gottfried sum rule, polarized structure function) and the
axial-vector coupling constant, where the pion fluctuation is believed to play
an important role.
