24 INTRODUCTION 



gence of Character. In the next chapter I shall discuss the com- 

 plex and little known laws of variation. In the five succeeding 

 chapters, the most apparent and gravest difficulties in accepting 

 the theory will be given : namely, first, the difficulties of transi- 

 tions, or how a simple being or a simple organ can be changed 

 and perfected into a highly developed being or into an elaborately 

 constructed organ; secondly, the subject of Instinct, or the mental 

 powers of animals ; thirdly. Hybridism, or the infertility of species 

 and the fertility of varieties when intercrossed ; and fourthly, the 

 imperfection of the Geological Record. In the next chapter I 

 shall consider the geological succession of organic beings through- 

 out time; in the twelfth and thirteenth, their geographical distri- 

 bution throughout space ; in the fourteenth, their classification or 

 mutual affinities, both when mature and in an embryonic condi- 

 tion. 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 unex- 

 plained 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 relations 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 dis- 

 passionate judgment of which I am capable, that the view which 

 most naturalists until recently entertained, and which I formerly 

 entertained — namely, that each species has been independently 

 created — is erroneous. I am fully convinced that species are not 

 immutable ; but that those belonging to what are called the same 

 genera are lineal descendants of some other and generally extinct 

 species, in the same manner as the acknowledged varieties of any 

 one species are the descendants of that species. Furthermore, I 

 am convinced that Natural Selection has been the most important, 

 but not the exclusive, means of modification. 



