PREFACE IX 



plied to tentative scientific hypotheses that disguise themselves 

 as dogmas. This criticism must come from within; but it can 

 only come from an outsider at the inside. 



If the title of the last chapter requires an explanation, I may 

 quote Webster's New Collegiate Dictionary: ''amphisbaena — a 

 fabled serpent with a head at each end, moving either way". 

 Whether strand separation was observed in the Middle Ages, is 

 not recorded. 



Columbia University Erwin Chargaff 



New York, N.Y. 

 December, 1962 



