PREFACE TO THE ENGLISH EDITION 



This work which appeared first in French in 1906 and 

 later in German and Italian now appears after some years 

 in English thanks to the interest shown by several Eng- 

 lish and American biologists and philosophers, who have 

 expressed a desire to have its circulation facilitated 

 among the savants of their countries. This new indica- 

 tion of the growing favor acquired in a short time by the 

 theories here advanced, notwithstanding the author's fear 

 that their novelty would stand somewhat in the way of 

 their reception, is the best reward he could desire for the 

 great difficulty he has encountered in the study of these 

 the most fundamental problems of biology. And he 

 wishes to pay here his sad and affectionate respect to the 

 revered memory of Professor C. O. Whitman, one of the 

 first to interest himself in this English edition, and at 

 the same time to express his gratitude to his friend Dr. 

 Basil Harvey for the great care which he has given to the 

 translation, as well as to Dr. Paul Carus and The Open 

 Court Publishing Co., who have been so good as to be- 

 come the publishers. 



Milan, March, 1911. E. R. 



