ON THE ORIGIN OF SPECIES. 
INTEODUCTION. 
When on board H.M.S. ^ Beagle/ as naturalist, I was 
much struck with certain facts in the distribution of the 
inhabitants of South America, and in the geological rela¬ 
tions of the present to the past inhabitants of that con¬ 
tinent. These facts seemed to me to throw some light 
on the origin of species—that mystery of mysteries, as 
it has been called by one of our greatest philosophers. 
On my return home, it occurred to me, in 1837, that 
something might perhaps be made out on this question 
by patiently accumulating and reflecting on all sorts of 
facts which could possibly have any bearing on it. After 
five years’ work I allowed myself to speculate on the 
subject, and drew up some short notes; these I enlarged 
in 1844 into a sketch of the conclusions, which then 
seemed to me probable: from that period to the present 
day I have steadily pursued the same object. I hope 
that I may be excused for entering on these personal 
details, as I give them to show that I have not been hasty 
in coming to a decision. 
My work is now nearly finished; but as it will take 
me two or three more years to complete it, and as my 
health is far from strong, I have been urged to publish 
this Abstract. I have more especially been induced 
to do this, as Mr. Wallace, who is now studying the 
B 
