One can easily imagine more brilliant science fiction anthologies from the two decades in question, but the editors certainly succeed in suggesting what kind of stuff was being published in sci-fi magazines during those years. The 1940s--chosen entirely from the pages of Campbell's Astounding--is perhaps the more pleasing of the two, though some of its eight selections have already been much anthologized: Asimov's witty ""Reason,"" with its Cartesian robot pursuing the implications of his own Cogito ergo sum; Fredric Brown's perennially annoying ""Arena,"" with its dauntless Bob Carson saving mankind in single combat against a fiendish alien; Simak's sad portrayal of a newly serene and pastoral Earth as the eventual ""Huddling Place"" of agoraphobes. Less familiar but more arresting is Paul Carter's ""The Last Objective,"" a remarkably complex story of subterranean warfare supervised by an ever-present ""psych corps."" There are also good representative stories by Hal Clement (""Fireproof""), A. E. Van Vogt (""Co-operate--Or Else!""), and Eric Frank Russell (""Hobbyist""), as well as Philip Latham's klunky end-of-the-world number (""The Xi Effect""). The 1950s is a bit more various (twelve selections from a handful of magazines) and shows a broadening of the genre's intellectual horizons, with a greater play of skepticism and curiosity--which often resulted in uneasy clashes between ends and means (as in interesting stories by James Schmitz and the gifted Katherine Maclean, who both needlessly trivialize good premises). But the decade also saw the much-remarked influence of Ray Bradbury (a rather didactic tut-tut about TV and regimentation), the first irreverences of Robert Sheckley (""Early Model""), promising ventures into parallel-universe terrain (Philip JosÃ‰ Farmer's marvelous Columbus yarn), and some groundbreaking attempts to study the psychological components of human destructiveness (Henry Kuttner's ""Two-handed Engine"" and--more unexpectedly--Howard Fast's ""The Large Ant""). There are other contributions of varying merit from Budrys, Clarke, Richard Matheson, and Jerome Bixby. Predictably, the most provocative and forward-looking selection is Cordwainer Smith's dazzling ""Scanners Live in Vain""; marred by a pat happy ending which the later Smith might have eschewed, it still has everything to teach most present concocters of cyborg stories. In sum, two sound anthologies put together with real historical insight.