ARTIFICIAL SELECTION. 1 33 



scendants from a common progenitor to diverge in char- 

 acter." * 



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 ex- 

 istence of this property rests the artificial breeding, or 

 selection by man, consciously and unconsciously exer- 

 cised from the earliest commencement of hunting and 

 agriculture, of which, as Darwin says, " the importance 

 mainly lies in the power of selecting scarcely appreciable 

 differences, which are nevertheless found to be trans- 

 missible, 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, be- 

 cause, 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 tol- 

 erably 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 mod- 

 erate beak, elongated legs and body, their oesophagus 



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

 the German text. He kept no copy of the original MS. 



