•i INTRODUCTION. 



trees, which has seeds that must be transported by 

 certain birds, and which has flowers with separate sexes 

 absolutely requiring the agency of certain insects to 

 bring pollen from one flower to the other, it is equally 

 preposterous to account for the structure of this parasite, 

 with its relations to several distinct organic beings, by 

 the effects 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 insisrht into the means of modification and co- 



o 



adaptation. At the commencement of my observations 

 it seemed to me probable that a careful study of domes- 

 ticated 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 Domesti- 

 cation. "We shall thus see that a lame 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 coo 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 favour- 



