  Most inhomogeneities in the chemical composition of GC stars are due to
primordial enrichment. The model today most credited is that the winds lost by
high mass Asymptotic Giant Branch (AGB) stars, evolving during the first
$\simlt$200Myr of the Clusters life, directly form a second generation of stars
with abundance anomalies. The best indirect hint towards this suggestion is the
recognition that some peculiarities in the Horizontal Branch (HB) stars
distribution (blue tails, gaps, anomalous luminosity slope of the flat part of
the HB) can be attributed to the larger helium abundance in the matter,
processed through Hot Bottom Burning, from which these stars are born. The
model has been reinforced by finding a peculiar main sequence distribution in
the cluster NGC 2808, which also has a bimodal HB distribution and an extended
blue tail: the excess of blue objects on the main sequence has been interpreted
as stars with very high helium. We remark that the RR Lyr distribution may be
affected by the helium spread, and this can be at the basis of the very long
periods of the RRab variables of the metal rich clusters NGC 6388 and NGC 6441,
longer than for the very metal poor Oosterhoff II clusters. These periods imply
that the RR Lyr are brighter than expected for their metallicities, consistent
with a larger helium abundance.
