Acknowledgment is made for permission to reprint the following material:

 

“The Chapter Ends,” by Poul Anderson. Copyright ©1953 by Columbia Publications. First published in Dynamic Science Fiction, January 1954. Reprinted by permission of the author.

 

“Watershed,” by James Blish. Copyright ©1955 by Quinn Publishing, Inc. First published in If, May 1955. Reprinted by permission of the author’s estate and the agents for that estate.

 

“Slow Tuesday Night,” by R. A. Lafferty. Copyright © 1965 by Galaxy Publishing Corporation. First published in Galaxy, April 1965. Reprinted by permission of the author and the author’s agents, the Virginia Kidd Literary Agency.

 

“Aye, and Gomorrah,” by Samuel R. Delany. Copyright ©1967 by Harlan Ellison for Dangerous Visions. First published in Dangerous Visions (Doubleday, 1967). Reprinted by permission of the author.

 

“Nobody’s Home,” by Joanna Russ. Copyright ©1972 by Robert Silverberg. First published in New Dimensions II (Doubleday, 1972). Reprinted by permission of the author.

 

“The Hero as Werwolf,” by Gene Wolfe. Copyright © 1975 by Thomas M. Disch. First published in The New Improved Sun (Harper, 1975). Reprinted by permission of the author and the author’s agents, the Virginia Kidd Literary Agency.

 

“Halfjack,” by Roger Zelazny. Copyright ©1979 by Omni Publications International, Ltd. First published in Omni, June 1979. Reprinted by permission of the author’s estate and the agents for that estate, the Pimlico Agency, Inc.

 

“Dancers in the Time-Flux,” by Robert Silverberg. Copyright © 1983 by Robert Silverberg. First published in Heroic Visions (Ace, 1983). Reprinted by permission of the author.

 

“Spook,” by Bruce Sterling. Copyright ©1983 by Mercury Press, Inc. First published in The Magazine of Fantasy & Science Fiction, April 1983. Reprinted by permission of the author.

 

“Understand,” by Ted Chiang. Copyright ©1991 by Davis Publications, Inc. First published in Asimov’s Science Fiction Magazine, August 1991. Reprinted by permission of the author and the author’s agents, the Virginia Kidd Literary Agency.

 

“None So Blind,” by Joe Haldeman. Copyright © Joe Haldeman. First published in Asimov’s Science Fiction, November 1994. Reprinted by permission of the author.

 

“Mortimer Grey’s History of Death,” by Brian Stableford. Copyright ©1995 by Bantam Doubleday Dell Magazines. First published in Asimov’s Science Fiction, April 1995. Reprinted by permission of the author.

 

“Brother Perfect,” by Robert Reed. Copyright ©1995 by Bantam Doubleday Dell Magazines. First published in Asimov’s Science Fiction, September 1995. Reprinted by permission of the author.

 

“A Child of the Dead,” by Liz Williams. Copyright © 1997 by Interzone. First published in Interzone, September 1997. Reprinted by permission of the author.

 

“Nevermore,” by Ian R. MacLeod. Copyright ©1997 by Ian R. MacLeod. First published in Dying For It (HarperPrism, 1997). Reprinted by permission of the author.

 

“The Wisdom of Old Earth,” by Michael Swanwick. Copyright ©1997 by Dell Magazines. First published in Asimov’s Science Fiction, December 1997. Reprinted by permission of the author.

 

“Toast: A Con Report,” by Charles Stross. Copyright ©1998 by Interzone. First published in Interzone, August 1998. Reprinted by permission of the author.

 

“The Gardens of Saturn,” by Paul J. McAuley. Copyright ©1998 by Interzone. First published in Interzone, November 1998. Reprinted by permission of the author.

 

“Grist,” by Tony Daniel. Copyright ©1998 by Dell Magazines. First published in Asimov’s Science Fiction, December 1998. Reprinted by permission of the author.

 

“Fossil Games,” by Tom Purdom. Copyright ©1999 by Dell Magazines. First published in Asimov’s Science Fiction, February 1999. Reprinted by permission of the author.

 

“The Wedding Album,” by David Marusek. Copyright ©1999 by Dell Magazines. First published in Asimov’s Science Fiction, June 1999. Reprinted by permission of the author.

 

“Steps Along the Way,” by Eric Brown. Copyright ©1999 by Eric Brown. First published in Moon Shots (DAW, 1999). Reprinted by permission of the author.

 

“Border Guards,” by Greg Egan. Copyright ©1999 by Interzone. First published in Interzone, October 1999. Reprinted by permission of the author.

 

“Homo Sapiens Declared Extinct,” by Bruce Sterling. Copyright ©1999 by Bruce Sterling. First published in Nature, 11 November 1999. Reprinted by permission of the author.

 

“A History of the Human and Post-Human Species,” by Geoffrey A. Landis. Copyright © 2000 by Geoffrey A. Landis. First published in Science Fiction Age, January 2000. Reprinted by permission of the author.

 

“The Great Goodbye,” by Robert Charles Wilson. Copyright © 2000 by Robert Charles Wilson. First published in Nature, 11 September 2000. Reprinted by permission of the author.