Wollheim Donald A., Ace Books, Inc., 1963
Introduction and story comments by Donald A. Wollheim. Includes: Child of the Sun, by Leigh Brackett; Sunrise on Mercury, by Robert Silverberg; By the Name of Man, by John Brunner; The Red Death of Mars, by Robert Moore Williams; The Planet of Doubt, by Stanley G. Weinbaum; and Tiger by the Tail, by Poul Anderson.