6 INTRODUCTION. 



throughout time; in the twelfth and thirteenth, their 

 geographical distribution throughout space; in the four- 

 teenth, their classification or mutual affinities, both when 

 mature, and in an embryonic condition. In the last 

 chapter I shall give a brief recapitulation of the whole 

 work, and a few concluding remarks. 



No one ought to feel surprise at much remaining as 

 yet unexplained in regard to the origin of species and 

 varieties, if he make due allowance for our profound 

 ignorance in regard to the mutual relations of the many 

 beings which live around us. Who can explain why one 

 species ranges widely and is very numerous, and why 

 another allied species has a narrow range and is rare? 

 Yet these relations are of the highest importance, for 

 they determine the present welfare and, as I believe, the 

 future success and modification of every inhabitant of 

 this world. Still less do we know of the mutual rela- 

 tions of the innumerable inhabitants of the world during 

 the many past geological epochs in its history. Although 

 much remains obscure, and will long remain obscure, I 

 can entertain no doubt, after the most deliberate study 

 and dispassionate judgment of which I am capable, that 

 the view which most naturalists until recently enter- 

 tained, and which I formerly entertained — ^namely, that 

 each species has been independently created — is errone- 

 ous. I am fully convinced that^speeies'arekTitit immuta- 

 ble; but that those belonging to what arte called the 

 same genera are lineal descendants of somje other and 

 generally extinct species, in the same ma/nner as the 

 acknowledged varieties of any one species\ are the de- 

 scendants of that species.l^ Furthermore, I am convinced 

 that Natural Selection has been the most important, hut 

 not the exclusive, means of modificatibrsr 



