My brother named his dog Trotsky: make of that what you will. :)

James, did humans survive on some of the Cobbly worlds they were seeded on, or do we just not know?

(Speaking of Cobbly worlds, I vaguely recall a story involving an investigator looking in on some scientists on Pluto or some such which have made contact with alternate worlds, with unpleasant results. There's some sort of mind-controlling moth singer and a painting which is actually a doorway to one of those worlds. There is a line about one of the scientists being "owned" by something monstrous. Does anyone recall if that is a Simak story, or am I thinking of a work by someone else?)