viii PREFACE 



which shall attempt to tell the tale of heredity. 

 There may be a certain advantage in having as 

 spokesman one who is not at present immersed in the 

 arduous technical investigations that are making 

 the tale worth telling. The difficulties in under- 

 standing this complicated subject may possibly be 

 realized better by one who is himself still struggling 

 with them, than by the seasoned expert who has 

 long since forgotten that such difficulties exist. 



Among others I am particularly indebted to Dr. 

 C. B. Davenport for many helpful suggestions, to 

 my colleague, Professor A. D. Mead, for reading the 

 manuscript critically, to Dr. S. I. Kornhauser who 

 gave valuable aid in connection with the chapter 

 on the Determination of Sex, and to my wife for 

 assistance in final preparation for the press. 



I wish to thank Professor H. S. Jennings and Dr. 

 H. H. Goddard, who have given generous permission 

 to copy certain diagrams, as well as The Outlook 

 Company and The Macmillan Company for the use 

 of figures 24 and 66, respectively. 



The fact that all the suggestions which were at 

 various tunes offered by my kindly critics have 

 not been incorporated in the text, absolves them 

 from responsibility for whatever remains. 



H. E. W. 



PROVIDENCE, R. I., 

 September, 1918. 



