# Astounding Science Fiction/Volume 44/Number 05

Reg. U. S. Pat. Off.
* CONTENTS
* JANUARY, 1950VOL. XLIV, NO. 5
* SHORT STORIES
* THE Xi EFFECT, by Philip Latham................................................................................................................................................................................................................................................................................................................................................................................................6
* UNDESIRABLE ALIEN, by David McCarthy................................................................................................................................................................................................................................................................................................................................................................................................24
* GYPSY, by Poul Anderson................................................................................................................................................................................................................................................................................................................................................................................................66
* NOVELETTES
* NOT TO BE OPENED—, by Roger Flint Young................................................................................................................................................................................................................................................................................................................................................................................................33
* OLE MOTHER METHUSELAH, by René Lafayette................................................................................................................................................................................................................................................................................................................................................................................................80
* ARTICLE
* MAXWELL'S DEMON AND MONSIEUR RANQUE, by Arthur C. Parlett................................................................................................................................................................................................................................................................................................................................................................................................105
* SERIAL
* ... AND NOW YOU DON'T, by Isaac Asimov................................................................................................................................................................................................................................................................................................................................................................................................111
* (Conclusion)
* READERS' DEPARTMENTS
* THE EDITOR'S PAGE................................................................................................................................................................................................................................................................................................................................................................................................4
* BOOK REVIEW................................................................................................................................................................................................................................................................................................................................................................................................153
* BRASS TACKS................................................................................................................................................................................................................................................................................................................................................................................................154
* IN TIMES TO COME................................................................................................................................................................................................................................................................................................................................................................................................162
* THE ANALYTICAL LABORATORY................................................................................................................................................................................................................................................................................................................................................................................................162
Editor JOHN W. CAMPBELL, JR. W2ZGU
Assistant Editor C. TARRANT
COVER BY BONESTELL
Illustrations by Cartier, Gaughan, Orban, Rogers and Ward
The editorial contents have not been published before, are protected by copyright and cannot be reprinted without publishers' permission. All stories in this magazine are fiction. No actual persons are designated by name or character. Any similarity is coincidental.
Monthly publication issued by Street & Smith Publications, Incorporated at 775 Lidgerwood Avenue. Elizabeth, New Jersey. Reentered as Second Class matter October 19, 1948 at the Post Office at Elizabeth, New Jersey, under Act of Congress of March 3, 1879. Copyright, 1949, in U. S. A. and Great Britain by Street & Smith Publications, Inc. Allen L. Grammer, Chairman of the Board; Gerald H. Smith, President; Henry W. Ralston, Vice-President and Secretary; Thomas H. Kaiser, Treasurer. Subscriptions to Countries in Pan American Union, $2.75 per year; $3.00 per year in Canada, elsewhere, $3.25 per year. All subscriptions should be addressed to P.O. Box 494, Elizabeth, N. J. We cannot accept responsibility for unsolicited manuscripts or artwork. Any material submitted must include return postage.
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NEXT ISSUE ON SALE JANUARY 18, 1950
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