INTRODUCTION. 



of external conditions, or of habit, or of the volition of the plant 

 itself. 



It is, therefore, of the highest importance to gain a clear insight 

 into the means of modification and coadaptation. At the commence- 

 ment of my observations it seemed to me probable that a careful 

 study of domesticated animals and of cultivated plants would offer 

 the best chance of making out this obscure problem. Nor have 

 I been disappointed ; in this and in all other perplexing cases I 

 have invariably found that our knowledge, imperfect though it be, of 

 variation under domestication, afforded the best and safest clue. I 

 may venture- to express my conviction of the high value of such 

 studies, although they have been very commonly neglected by 

 naturalists. 



From these considerations, I shall devote the first chapter of this 

 Abstract to Variation under Domestication. We shall thus see that 

 a large amount of hereditary modification is at least possible ; and, 

 what is equally or more important, we shall see how great is the 

 power of man in accumulating by his Selection successive slight 

 variations. I will then pass on to the variability of species in a 

 state of nature ; but I shall, unfortunately, be compelled to treat 

 this subject far too briefly, as it can be treated properly only by 

 giving long catalogues of facts. We shall, however, be enabled to 

 discuss what circumstances are most favourable to variation. In 

 the next chapter the Struggle for Existence amongst all organic 

 beings throughout the world, which inevitably follows from the 

 high geometrical ratio of their increase, will be considered. This is 

 the doctrine of Malthus, applied to the whole animal and vegetable 

 kingdoms. As many more individuals of each species are born than 

 can possibly survive; and as, consequently, there is a frequently 

 recurring struggle for existence, it follows that any being, if it vary 

 however slightly in any manner profitable to itself, under the com- 

 plex 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 Diver- 

 gence of Character. In the next chapter I shall discuss the complex 

 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 transitions, or how a 



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