PREFACE 9 



to Macaulay, who took advantage of the opportunity 

 with his usual ruthlessness and lack of any sense of fair 

 play where his preconceived ideas and middle-class pre- 

 judices were concerned. Saddler brought together a 

 bulky, and in some parts valuable, body of evidence 

 bearing on the subject in his two volumes, but his 

 formula does not call for extended criticism. 



The best hypotheses yet put forward in the effort to 

 explain the law governing fertility, known to the writer, 

 are those of Doubleday and Herbert Spencer. They are 

 analysed and criticised in the body of this work. 



During later years a hypothesis has been developed 

 by Dr. John Brownlee that the declining birthrate is the 

 result of a recurrent fluctuation of " germinal vitality." 

 His theory is that there are vast periodical fluctuations 

 of fertility, and that periods of high fertility, which he 

 identifies with periods of high germinal vitality, are 

 accompanied by the birth of large numbers of great men ; 

 while during periods of low germinal vitality, or low 

 fertility, great men are rare. Dr. Brownlee illustrates 

 the theory with a large body of interesting facts and 

 statistics. The weaknesses of the hypothesis lie chiefly 

 in the facts that there is very little reliable evidence 

 bearing upon birthrate fluctuations in past ages, as periods 

 of racial expansion are not necessarily due to a high 

 birthrate ; that estimates of the relative greatness of the 

 men who appear at different epochs are largely a matter 

 of individual taste, " greatness " being, in a large pro- 

 portion of cases, merely the result of exceptional luck 

 in the advertising line, or " the flatness of the surround- 

 ing country " ; that the theory is not a necessary de- 

 duction from the principles of organic evolution, its 

 relation to which is not explained ; and that it offers 

 no clue to the mechanism which controls fertility. 



