vi THE EVOLUTION OF LIFE 
capacity as a comparatively young physician, I felt 
compelled to renounce these investigations for a time 
and to devote all my energies to professional work. 
The last article written by me on the subject of 
Archebiosis appeared in The Neneteenth Century 
for February 1878, in reply to one from Professor 
Tyndall. 
Since that date I have published nothing on this 
subject except a single chapter last year in my work 
“The Nature and Origin of Living Matter.” Still, 
though nothing had been published, I had, in the 
intervening years—from time to time, when oppor- 
tunity permitted—done a good deal of work in 
reference to this question. 
After having devoted most of my energies to 
professional and teaching work during the following 
twenty years, | resigned my teaching appointments 
at University College and Hospital at the beginning 
of 1898, in order that all the time and energy that 
could be spared from private practice might then be 
devoted to a reinvestigation of the subject of 
Heterogenesis, concerning which I had been silent 
since 1872. 
The fact of my silence for the previous twenty 
years on both subjects may well have given colour 
to the notion, probably entertained by many, that I 
had been defeated and had given up the cause. 
Meanwhile the most extraordinary advances had 
been made by bacteriologists in many parts of the 
world, resulting in an increase of knowledge of vast 
importance for the science of medicine, and of a kind 
which doubtless seemed to many only compatible 
