ARTIFICIAL SELECTION. I33 



descendants from a common progenitor to diverge in 

 character."* 



That organisms are variable and not fixed in rigid 

 forms, is a phenomenon so general that variability passes 

 current as a self-evident property of organic existence. 

 In the next chapter we shall inquire how far everything 

 organic is necessarily subject to mutability. On the 

 existence of this property rests the artificial breeding, 

 or selection by man, consciously and unconsciously 

 exercised from the earliest commencement of hunting 

 and agriculture, of which, as Darwin says, "the impor- 

 tance mainly lies in the power of selecting scarcely 

 appreciable differences, which are nevertheless found to 

 be transmissible, and which can be accumulated until the 

 result is made manifest to the eye of every beholder." 

 In the " Origin of Species," as an example of methodic 

 selection in the production of breeds, Darwin has chosen 

 the pigeon, to the breeding of which he zealously devoted 

 himself for many years. 



The pigeon is specially adapted to the purpose of 

 scientific observation of the phenomena of breeding, 

 because, owing to its monogamic habits, it is easy to 

 control, because it may be brought in a short time to 

 striking variations, because the records of its breeding 

 are tolerably complete, and, finally, because it is one of 

 the few domestic animals of which the ancestral stock 

 is scarcely open to a doubt. 



The chief races produced by the fanciers may be 

 grouped as follows. The Pouter Pigeons have a 

 moderate beak, elongated legs and body, their ceso- 



* Mr. Darwin has himself been good enough to re-write his letter from the 

 German text. He kept no copy of the original M S. 



