  We discuss three possible scenarios for the interpretation of mesons
containing a heavy quark and its antiquark near and above the first threshold
for a decay into a pair of heavy mesons in a relative $S$--wave. View I assumes
that these thresholds force the quark potential to flatten which implies that
while in these energy ranges molecular states may be formed there should not be
any quark--anti-quark states above these thresholds. View II assumes that the
main part of the interaction between two mesons is due to the poles which
originate from the $Q\bar Q$ interaction. The properties of the $Q\bar Q$
mesons are strongly influenced by opening thresholds but the number of states
is given by the quark model. In View III, both types of mesons are admitted
also near and above the open flavor thresholds: $Q\bar Q$ mesons and
dynamically generated mesons. Experimental consequences of these different
views are discussed.
