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. 
