m PREFACE 



physiological genetics. Needless to say, the reader is Bupposed 

 to have sufficienl knowledge of genetics and embryology. 



The author takes pleasure in expressing his gratitude to 

 Professor E. B. Babcock, who was so kind as to go carefully over 



the whole manuscript; also to those publishers who permitted 

 me to copy figures. 



Richard Goldschmidt. 

 (M\ BBS] rv of California, 

 Berkeley, Calif., 

 January, 1938. 



