Darn, I had his name wrong and fixed it, but somewhere an undo button must have been hit. Thanks for pointing it out.
I'm more than happy to add corrections to an already "longer than zero" list of errata. I'll give the Scheme chapter and Wikipedia a once-over to see where I went off the rails.
There's also an issue where Hewitt's actors were more like Erlang processes, i.e. unlike Scheme closures, they could run independently of each other. Maybe call/cc can simulate something like that. I remember the footnote in SICP claiming that Scheme was developed partly to understand what Hewitt was talking about, but I think that might not have been serious. It could be worth trying to talk to Steele or Sussman about this history.
Yup, and the book mentions that, including the surprising result that (Hewitt-style) actors - which are not completely like Erlang processes - and Scheme's closures were the same.