THE DOMESTIC PIGEON 373 



Relation to Environment. The oval form of the pigeon is 

 well adapted to cleaving the air, and the feathers form a light 

 waterproof covering which serves to retain the body-heat in 

 the rapid flights in the cold atmosphere. A bird has been 

 termed " an ocean greyhound in miniature," and the compar- 

 ison is not inapt for a creature which possesses such powers 

 of flight and maintains so high a temperature. " It is worthy 

 of notice," say Parker and Haswell, " that birds agree with 

 insects, the only other typically aerial class, in having the 

 inspired air distributed all over the body, so that the aeration 

 of the blood is not confined to the limited area of an ordinary 

 respiratory organ." Other important structural peculiarities 

 are the light, toothless beak, and the small number of digits 

 in the anterior extremities. Still other characters have been 

 referred to in the discussion of the internal anatomy. 



The many varieties of the domestic pigeon afforded Darwin 

 much material for his book, The Variations of Animals and 

 Plants under Domestication. From their study he obtained 

 many of the conclusions which led to the statement of the 

 principle of natural selection. These domestic varieties differ 

 among themselves in appearance far more than many species 

 in nature. Some well-known varieties are the pouters, fan- 

 tails, tumblers, and carriers. The pouters are large birds with 

 elongate body and legs, and often with inflated crop and 

 oesophagus. The fan tails are known by the extraordinary 

 development of tail-feathers. The tumblers have the remark- 

 able habit of turning somersaults backward in the air from a 

 considerable height nearly to the ground. The carriers have 

 the " homing faculty " developed to such an extent that they 

 are useful as messengers. Though shut within a basket and 

 removed long distances from their home, they have been able 

 to find their way back. Carriers have been used by man for 

 many centuries, notably within recent times at the siege of 

 Paris and in the Russo-Japanese War. 



