Who is Sherkaner Underhill from A Deepness in the Sky and what is their importance?

Sherkaner Underhill is a spider and something of a dreamer. He has lots of ideas about research to be used by the military, but he also has a short attention span. Sherkaner is a free-thinker, who believes that he should be free from the dictates of society. Over the course of the novel, he and Victory Smith marry and have six out-of-phase children. In the end, Sherk disappears and is never seen again.