4, INTRODUCTION. 



seeds that must be transported by certain birds, and 

 wliich has flowers with separate sexes absolutely re- 

 quiring 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 insight into the means of modification and co- 

 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 per- 

 plexing cases I have invariably found that our knowl- 

 edge, imperfect though it be, of variation under domes- 

 tication, 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 ne- 

 glected 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 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 favour- 



