I suppose this is old bits, but they're new and fun to me:
"But back to growth patterns. Natural pearls grow in layers too,
around a grain of sand that irritates the oyster in question, which
forms layers of pretty stuff. This could be the cross-section of a
pearl. People cut up onions frequently, but they almost never cut
up pearls. So it's even truer of pearls than of onions. The outer
layer is the most important. It's what people see. Or if the pearl is
still growing, it's the layer that will support the layer after it. I
realize that that classifies me as a mere irritant. I am content to be
so classified. "
excerpt from
http://www.perl.com/pace/pub/perldocs/1998/08/show/onion.html
-- Dan Connolly http://www.w3.org/People/Connolly/