PREFACE XV 



English biologists, after the brilliant paradox of 

 Weismann, which asserts that acquired characters 

 are not and never can be inherited, and as will be 

 seen later (p. 266 infra), he classes this with 

 the hypothesis of Nageli, that every individual 

 is endowed with an innate tendency towards 

 perfection, as theories on which no agreement 

 between naturalists seems even probable. His 

 method, too, as shown in the book of which 

 the following pages are a translation, seems to be 

 not only the best possible, but the only one which 

 can convey to the general reader a fair idea of the 

 problems set before him in a reasonably limited 

 space. In the First Part of the book, he gives a 

 summary of the work of the principal authors of 

 the evolutionist theory, including therein Darwin's 

 precursors as well as his successors, and in the 

 Second Part he deals with the different processes 

 of the variation and the extinction of species, to- 

 gether with the effect of migrations, and the in- 

 teresting problem of the first appearance of life on 

 our globe. That the work is well abreast of modern 

 research is, I think, evident from the space he 

 devotes to the " saltation " theory of de Vries and 

 Nilsson, and from his remarks on the light likely 

 to be thrown on the earliest forms of life by the 

 exploration of the Polar regions now in progress. 

 It only remains to be said that the two tables of 



