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PREFACE TO THIRD EDITION 



THIS book, originally published in 1907, is intended as an intro- 

 duction to the study of heredity, a subject of fascinating interest 

 and of great practical importance. In recent years much pro- 

 gress has been made in the scientific study of heredity, and, as 

 the literature is widely scattered and often very technical, there 

 may be utility in an exposition which aims at being comprehen- 

 sive and accurate, and yet relatively simple. The bibliography 

 will enable serious students to fill in details, and follow up clues. 

 It is arranged with a subject-index, so that the literature dealing 

 with particular points can be seen at a glance. 



The book has aimed at a fair-minded treatment of the numerous 

 debatable questions, for it is too soon to settle down to fixed 

 conclusions on more than a few points. An attempt has been 

 made to keep practical problems in view, but it has not been 

 found advisable to risk many concrete suggestions. In most 

 cases we do not as yet know or understand enough to warrant 

 more than a general recommendation to take thought for the 

 morrow by considering the ideal of Eugenics. 



A glance at the book will show that prominence has been 



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