/ INTRODUCTION ""'"' J^^J 



considered. This is the dootriae of Malthus, applied to 

 the whole animal and vegetable kingdoms. As many- 

 more individuals of each species are born than can possi- 

 bly survive; and as, consequently, there is a frequently 

 recurring struggle for existence, it follows that any 

 being, il it vary however slightly in any manner profita- 

 ble to itself, under the complex and sometimes varying 

 conditions of life, will have a better chance of surviving, 

 and thus be naturally selected. 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 the 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 Char- 

 acter. In the next chapter 1 shall discuss the complex 

 and little known laws of variation. In the five succeed- 

 ing chapters, 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 sim- 

 ple 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 Eecord. In 

 the next chapter I shall consider the geological succes- 

 sion of organic beings throughout time; in the twelfth 

 and thirteenth, their geographical distribution throughout 

 space; in the fourteenth, their classification or mutual 

 affinities, both when mature and in an embryonic con- 



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