viii PREFACE 



footsteps of the parent. Unless it were true there could be 

 no development of the individual and no evolution of the race. 

 This fifth chapter is the crux of the whole work. If the 

 scientific reader finds its reasoning correct and its conclusions 

 valid, he will probably not raise much objection to the rest of 

 the book. 



I have addressed the volume mainly to medical men. The 

 evidence relied on is drawn largely from medical sources; 

 medical men form the largest body of scientific workers ; they 

 deal constantly with questions of Heredity, a knowledge of 

 which is of great importance to them ; but in a measure they 

 have neglected the systematic study of the subject. Little or 

 no direct instruction in it is given to medical students. There 

 does not exist even a text-book to which they may refer. But 

 a knowledge of Heredity is becoming essential to the educated 

 doctor. I have sought to supply the want. I hope, however, 

 the professional biologist and the general reader will not find 

 the work devoid of interest. I have tried throughout to give 

 prominence to broad generalizations rather than to isolated 

 facts, to found my conclusions wholly on verified evidence, 

 and to write in such a way that the reader's task will not 

 be unnecessarily toilsome. 



My hearty thanks are due to Dr. Gerald Leighton for 

 " going over " the first fifteen chapters, and to the Editors of 

 The Monthly Review and The Lancet for permission to adapt 

 for Chapter X. matter which had appeared in their pages. 



