I managed to get most of my set homework for Friday's class done on the weekend. That gave me time to play. The idea of the egg has stuck with me. I decided to give my imagination a bit of help and constructed an egg-shaped spiral out of beading wire.
Looking at the 3-D form in reality made it easier to explore the lines which might represent it--especially when the form was already indicated by what is essentially a line. The shadows are something else again. And of course the wire is three dimensional, so reflections off the curved surface add another layer of complication.