  The fragmentation of quasi-projectiles from the nuclear reaction
$^{40}$Ca+$^{12}$C at 25 MeV per nucleon bombarding energy was used to produce
$\alpha$-emission sources. From a careful selection of these sources provided
by a complete detection and from comparisons with models of sequential and
simultaneous decays, evidence in favor of $\alpha$-particle clustering from
excited $^{16}O$, $^{20}Ne$ and $^{24}Mg$ is reported.
