PREFACE 



In pi.ANMNG the syniposiuiii on which this volume is based, an 

 attempt was made to present the evidence for "sex" in the principal 

 groups of micr(K)rganisms, from the viruses through bacteria, func^i, 

 and unicellular algae to the protozoa. Since the material \vhich could 

 be presented in the short time afforded by the two sessions devoted 

 to the symposium was necessarily limited in scope, an effort has been 

 made in this volume to expand to some extent the ground covered at 

 the symposium itself. 



Dr. Msconti discusses evidence for recombination of "genes" in 

 \iruses without claiming that the phenomena demonstrate sex for that 

 group. Dr. Lederberg and Dr. Tatum review genetic evidence for 

 "sex" in the bacteria, and Dr. Hutchinson and Dr. Stempen describe 

 cell fusions in certain bacteria. These cell fusions could provide an 

 opportunity for the recombinations of genes that have been indicated. 

 Next, Dr. Raper offers a comprehensive coverage of sex in the fungi 

 and the many variations in sex phenomena found in that group. 



Passing on to the lower algae, Dr. Patrick describes syngamy in 

 diatoms and Dr. Lewin reviews the sexuality of other unicellular 

 algae, especially the flagellates. 



Next is a review of sexual phenomena in the protozoa, with 

 sections on the Mastigophora, the Sarcodina, the Sporozoa, and the 

 Ciliophora. At the symposium. Dr. Cleveland reported on his studies 

 of sexual reproduction among the flagellates living in the gut of the 

 wood-feeding roach, Cryptocerciis pimctulatus, but he did not find 

 it possible to provide a paper for the volume. Consequently, a review 

 of his published papers on that subject follows the section devoted 

 to the Mastigophora. 



After the section on sex in the CiHophora, Dr. Nanney sum- 

 marizes the status of mating type phenomena in Faramecium aiirelia 

 and then presents certain new^er interpretations of mating type behav- 

 ior that have evolved in Dr. Sonneborn's laboratory at Indiana Uni- 

 versity. This paper is followed by Dr. Metz's discussion of mating 

 type substances, with a comparison of the conditions found in Fara- 

 mecium and other ciliates wdth those found in the Metazoa. 



At the end of the volume is a short section devoted to comments 



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