Page - 24 - in The Origin of Species

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.