28 THE ORIGIN OF SPECIES 



terous to account for the structure of this parasite, with 

 its relations to several distinct organic beings, by the 

 eilects of external conditions, or of habit, or of the voli- 

 tion of the plant itself. 



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

 clear insight into the means of modification and coadap- 

 tation. At the commencement of my observations it 

 seemed to me probable that a careful study of domesti- 

 cated 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 per- 

 plexing cases I have invariably found that our knowledge, 

 imperfect though it be, of variation under domestication, 

 afforded the best and safest .clew. I may venture to ex- 

 press 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 Domestica- 

 tion. 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 spe- 

 cies 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 favorable to variation. In the 

 next chapter the Struggle for Existence among all organic 

 beings throughout the world, which inevitably follows 

 from the high geometrical ratio of their increase, will be 



