THE DOMESTIC PIGEON 375 



The Reproductive System. The spermaries (Fig. 195) are 

 oval bodies attached to the kidneys. The ovary of the right 

 side is not developed, but the left ovary is a large organ 

 situated near the kidneys. 



Development. Unlike most of our domestic animals, 

 pigeons choose their mates for life. After fertilization the 

 ova, or " yolks," pass down the oviduct and are covered with 

 secretions from glands in different regions, first with the 

 white, or albumen, then with a thin membrane, and lastly 

 with a white, limy shell. The eggs are laid in a roughly 

 made nest, and are incubated by both parents in turn for 

 about two weeks, when they hatch. The young bird breaks 

 through the shell by means of a hard structure on the tip of 

 its beak, and makes its appearance covered with a fine down. 

 It is interesting to note in this connection that Darwin says 

 that some of the short-beaked tumbler pigeons, which have 

 been developed by artificial selection, have beaks so short 

 that they are unable to get out of the shell alone, and re- 

 quire therefore to have the help of the pigeon-fanciers. For 

 a few days after hatching, the young bird is fed by both 

 parents with a milky secretion afforded by the crop and 

 called "pigeon's milk/' 



At first the young are deaf and the eyes are closed, but 

 both sight and hearing are acquired within a few days. The 

 young birds rapidly acquire the power to make coordinated, 

 or connected, muscular movements, and in a few days the 

 voice develops. The independent life of the pigeon, in some 

 cases, begins about the thirty-fourth day after hatching. 



Relation to Environment. The 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. "It is worthy of 

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

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



