Published online by Cambridge University Press: 14 August 2015
It is pointed out that the metallicity of galactic and extragalactic globular clusters correlates with the density of the regions in which they were formed. Within individual galaxies the regions of highest density have the highest metallicity.
Some of the differences in family traits between the globulars in the Andromeda Nebula, the Galaxy and the Magellanic Clouds might be understood if the M31 cluster system is ~ 1 × 109 yr older and the SMC cluster system ~ 1 × 109 yr younger than galactic globular clusters.