Preface ix 



Robert P. Wagner, Norman K. WesselLs, and Charles Yanofsky. 

 Theodosius Dobzhansky read and criticized the entire book. Tliis 

 generous donation of time and effort on the part of all these indi- 

 viduals is deeply appreciated. Many of the subjects considered here 

 have been discussed in detail with colleagues and students in our 

 Population Biology Seminar. The authors accept full responsibilitv 

 for all errors of fact and interpretation, as they have not always been 

 able to adopt the suggestions of the reviewers. 



Paul R. Ehrlich 

 Richard \V. llnhn 



