  Spherically symmetric solutions with a flux of electric and magnetic fields
in Kaluza-Klein gravity are considered. It is shown that under the condition
(electric charge $q$) $\approx$ (magnetic charge $Q$) ($q>Q$) these solutions
are like a flux tube stretched between two Universes. The longitudinal size of
this tube depends on the value of $\delta = 1 - Q/q$. The cross section of the
tube can be chosen $\approx l_{Pl}$. In this case this flux tube looks like a
1-dimensional object (thread) stretched between two Universes. The propagation
of gravitational waves on the thread is considered. The corresponding equations
are very close to the classical string equations. This result allows us to say
that the thread between two Universes is similar to the string attached to two
$D-$branes.
