viii PREFACE 



inquiry is not ripe for more than a general recommendation to 

 take thought for the morrow by considering the ideal of Eu- 

 genics. 



A glance at the book will show that much prominence has 

 been given to three kinds of conclusions — those reached by 

 microscopic study of the germ-cells, those reached by the appli- 

 cation of statistical methods, and those reached through ex- 

 periment. I have equal sympathy with all these ways of 

 attacking the mysterious problems, and since I have not, to 

 my lasting regret, found any opportunity, amid the continuous 

 claims of professional duties, of working along any one of them, 

 I can, without seeming to recommend my own wares, press a 

 consideration of the results which have been achieved on the 

 attention of all thoughtful men and women. The new facts 

 are of especial interest to medical practitioners, to educationists, 

 including clergymen, to social reformers, and to actual or 

 prospective parents. 



I have, throughout, acknowledged my indebtedness to autho- 

 rities, and the bibliography (which is merely representative) 

 shows how many fields there are from which to glean. In 

 particular, I have been indebted to the works of Galton, Weis- 

 mann, Pearson, Bateson, and De Vries. 



I have to thank my friends Mr. E. S. Russell and Dr. John 

 Rennie for going over the proofs, and saving the pages from 

 many mistakes. Dr. Leslie Mackenzie was kind enough to 

 read the chapter on Heredity and Disease, and some of his 

 helpful suggestions have been incorporated. I have to thank 

 Professor C. Correns and Professor H. E. Ziegler for generously 

 allowing me to copy four admirable diagrams ; also Mr. Young 

 Pentland and the Waiter Scott Publishin-g Company for allowing 



