x PREFACE 



here presented are, we believe, accurate to a high de- 

 gree. It is true that we have made rather dogmatic 

 statements and have drawn conclusions that do not 

 seem scientifically warranted from the data. We have 

 done this because it seems necessary to make these 

 statements and conclusions for the benefit of the lay 

 reader, and it was impossible to present in this book 

 all of the data that would substantiate them. We have, 

 as a matter of fact, drawn upon the material which is 

 soon to be presented in a larger book. The reference 

 to Mendelism is an illustration of what we mean. It 

 is, as it is given here, meager and inadequate, and the 

 assumption that the given law applies to human hered- 

 ity is an assumption so far as the data presented are 

 concerned. We would ask that the scientist reserve 

 judgment and wait for the larger book for the proof of 

 these statements and for an adequate discussion of 

 Mendelism in relation to the problem. 



The necessary expense for this study, as well as for all 

 of the work of the Research Laboratory, has been met 

 by voluntary contributions from philanthropic men and 

 women, who believe that here is an opportunity to 

 benefit humanity, such as is hardly equaled elsewhere. 



We take this means of expressing to them our deep 

 appreciation of their sympathy and generosity. I wish 



