ARTIFICIAL AND NATURAL SELECTION 33 



(vii.) All domestic pigeons resemble Columba livia 

 in their habits. They all lay two eggs, and require 

 the same time for hatching. They prefer the same 

 food, and coo in the same peculiar manner, unlike 

 other wild pigeons. 



(viii.) Columba livia has been proved to be capable 

 of domestication in Europe and in India. 



(ix.) Historical Evidence. — Referring to Aldro- 

 vandi, who figured pigeons in the year 1600, we 

 find the Jacobin with a less perfect hood; the Turbit 

 apparently without its frill ; the Pouter with shorter 

 legs, and a less remarkable bird in all respects ; the 

 Fantail with fewer tail feathers, and a far less 

 singular appearance ; the Tumbler existed then, but 

 none of the short-faced forms ; the Carrier had a 

 beak and wattle far less developed than the modern 

 English Carrier. These were the same groups of 

 pigeons, but with their distinctive characters less 

 marked, thus showing convergence towards their 

 common ancestor. 



The mode of action of these changes is by 

 artificial selection, or the power possessed by man 

 of influencing the shape, size, and colour of animals 

 by the accumulation of small differences in successive 

 generations. This depends on two laws : 



1. The Law of Variation, depending on the fact 

 that no two animals are exactly alike. 



2. The Law of Inheritance, or the tendency to 

 hand down characters and peculiarities to de- 

 scendants. 



!- Domestic Poultry. — These afford another good 

 example of artificial selection. (See Fig. 2.) 



c 



