118 Dynamic Theory. 



Pouter has a much elongated body, wings and legs, and an enormously 

 developed crop, which it puffs out with air. The Tumblers have a 

 habit of flying in a compact flock high in the air, and there tumbling 

 heels over head in their flight. The Carrier, the Runt, the Barb and 

 others, all differ from each other in various ways. 



The differences in the skeletons of pigeons changed by artificial selec- 

 tion and cultivation, are of the most marked sort. There is great dif- 

 ference ' in the number of vertebrae and ribs, in the size and shape of 

 the gaps in the breastbones," and in the clavicles or wish-bone, in the 

 head and facial bones, the lower jaw, &c. In the Fan tail, which carries 

 its tail feathers erect and even curved forward so as to touch the head, 

 the oil gland is quite aborted. These radical anatomical differences are 

 proofs of the formative action of habit on the organism. 



A new species of rabbit has arisen on the island of Porto Santo, near 

 Madeira, since the year 1419, at which time a few tame Spanish rabbits 

 were left there. They are extraordinarily wild, of a rat-like shape, and 

 peculiar color, nocturnal in habit and will not breed with the European 

 species from which they were derived. 



The same effects are seen not only in the selective action upon the 

 domestic animals but upon plants. Almost all the cultivated fruits and 

 other vegetation have been greatty altered from their originals by re- 

 peated selection. This selection has been accomplished generally with- 

 out any well defined or highly scientific ideas or plan, but simply by 

 planting the seeds of the most satisfactory plants an obvious thing, 

 even to savages. 



This artificial selection, with its accompanying improvement of plants 

 and animals, is made by man for his own advantage. It shows the 

 flexibility of the conditions of life, and how there may be a constant ac- 

 cumulation of variations in one direction, amounting to specific distinc- 

 tions at first and generic distinctions at last. 



Artificial operations are, it is true, only a subdivision of natural ope- 

 rations, but artificial selection differs from the other natural selection in 

 the fact that, in the latter, the changes in the form of the organism are 

 made exclusively for its own benefit, while in the former, changes are 

 made for its benefit so as to include man's benefit. In the latter, the 

 organism maintains its struggle with its environment alone, in the 

 former, man constitutes a part of its environment and a very advan- 

 tageous and important part. For without doubt none of the proteges of 

 man would be the same without his help, but would speedily revert to- 

 ward the condition from which he has developed them. Witness the 

 hogs of Missouri, turned out to make their own living in the woods. 

 Long of limb, tail, ears, and snout, they are sinewy, enterprising, ac- 

 tive and hardy, able to climb an eight rail fence or crawl through a four 



