PREFACE ix 



defined, and are based on much accurate knowledge 

 of organic structure and development. The germ 

 plasm of the race is a uniquely precious material, 

 and its conservation and improvement in each genera- 

 tion should be the first aim of the State. The first 

 essential for such a conservation is the recognition of 

 the inherent (inherited) differences in the capacities 

 of individuals. Everything goes to show that once 

 a particular strain of germ plasm is lost, it is gone for 

 ever. In State recognition of the value of human 

 germinal qualities, perhaps no country has equalled 

 Sweden, where family records and genealogies have 

 been kept for centuries in an exceptionally complete 

 form, and where race biology is already recognised as 

 a subject of the greatest national importance. 



While it is necessary to recognise the fundamental 

 importance of inherited physical and mental differ- 

 ences, as the foundation of Eugenics, one must 

 also remember that environment counts in the sense 

 that a favourable or suitable environment is required 

 to bring out the potential qualities of any develop- 

 ing organism. Nevertheless, it is these potential 

 (germinal) differences on which the Eugenist must 

 rely in any effort to improve the race or direct the 

 selection of germinal qualities which is going on in 

 every generation. 



In conclusion, I wish to thank those who, in various 

 ways, have contributed to the production of this 

 book. I am indebted to Professor R. C. Punnett, 

 F.R.S., for permission to publish Figs. 4, ii, and 12, 

 from the Journal of Genetics ; to Sir Arthur Keith, 

 F.R.S., for the loan of the blocks from the Journal of 

 Anatomy and Physiology, January, 191 6, which 

 illustrate Figs. 13 and 14; to the Royal Society of 

 Medicine for permission to reproduce Fig. 15 (from 

 Proc. Roy. Soc. Med. {Path.), vol. x., p. 60); and to 

 the editorial board of the Journal of Heredity, for 



