  It is argued that the observed enhancement of the hadronic transition
Upsilon(4S) -> Upsilon(1S) eta relative to Upsilon(4S) -> Upsilon(1S) pi pi can
be explained if the resonance Upsilon(4S) contains an admixture of a four-quark
component, possibly due to the coupling to the meson channel B \bar B. A test
of the discussed mechanism by searching for the transition Upsilon(4S) ->
Upsilon(1S) eta'(958) is suggested. Some properties of possible four-quark
states related to the suggested one by the heavy quark spin symmetry are also
discussed.
