20 INTRODUCTION. 



to itself, under tlie complex and sometimes varying conditions 

 of life, uill have a better chance of survivinq-, and thus be nat- 

 la'cdhj sdectcd. From the strong principle of inheritance, any 

 selected variety will tend to propagate its new and modified 

 form. 



This fundamental subject of Natural Selection will be 

 treated at some length in tlie fourth chapter ; and we shall 

 then see how Natural Selection almost inevitably causes much 

 Extinction of the less improved forms of life, and leads to what 

 I have called Divergence of Character. In the next chapter I 

 shall discuss the com2:)lcx and little-known laws of variation. 

 In the four succeeding chajitcrs, the most apparent and gravest 

 difficulties in accepting the theory will be given : namely, first, 

 the difficulties of transitions, 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 va- 

 rieties when intercrossed ; and fourthly, the imperfection of 

 the Geological Record. In the next chapter I shall consider 

 the geological succession of organic beings throughout time ; 

 in the eleventh and twelfth, their geographical distribution 

 throughout space ; in the thirteenth, their classification or mu- 

 tual atlinities, both when mature and in an embrj-onic 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 

 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. AVho can explain why one species ranges Avidely and is 

 very numerous, and why another allied species has a narrow 

 range and is rare ? Yet these relations are of the highest im- 

 ]')ortance, for they determine the present welfare, and, as I be- 

 lieve, the future success and modification of every inhabitant 

 of tins world. Still less do we know of tlic mutual relations 

 of the innumerable inhabitants of the world during tlie man}"- 

 past geological epochs in its history. Although much remains 

 obscure, and Avill long remain obscure, I can entertain no 

 doubt, after the most deliberate study and dispassionate judg- 

 ment of which I am cajiable, that the view which most natu- 

 ralists entertain, and which I fonnerly entertained — namely, 

 that each species has been independently created — is erio- 



