A VOLUME IN THE WILEY 

 BIOLOGICAL RESEARCH SERIES 



This Series includes a number of small volumes 

 covering various topics in biology. The purpose is 

 to provide other scientists with an authoritative ori- 

 entation in the author's work as quickly as possible. 

 To provide this orientation, each author will be asked 

 to stress his own work and his own viewpoints without 

 loss of proper perspective of the field as a whole. 



ADVISORY BOARD 



Paul A. Weiss, PJi.D. 

 Professor of Zoology, University of Chicago 



David R. Goddard, Ph.D. 

 Professor of Botany, University of Pennsylvania 



Francis 0. Schmitt, Ph.D. 



Professor and Head, Department of Biology, 



The Massachusetts Institute of Technology 



Previously Published 



Anderson • Introgressive Hybridization 

 Lwoff • Problems of Morphogenesis in Ciliates 



