CHARACTERS AND HABITS OF BIRDS I/ 



Development of the egg. The method of the formation of an 

 egg is very interesting. It is the same in all birds, but is most 

 conveniently studied in fowls. If a laying hen is killed and the 

 body is opened so that the internal organs can all be seen, one 

 of the most conspicuous of these is a large, convoluted duct 

 having its outlet at the vent. In this duct, which is called the 

 oviduct, are eggs in various stages of formation. At its upper 

 extremity, attached to the backbone, is a bunch of globular yel- 

 low substances which are at once identified as yolks of eggs in 

 all sizes. The organ to which these are attached is the ovary. 

 The smallest yolks are so small that they cannot be seen with- 

 out a powerful microscope. These yolks are not germs, but as 

 they grow the germ forms on one side of each yolk, where it 

 appears as a small white spot. 



When a yolk is full-grown it drops into the funnel-shaped 

 mouth of the oviduct. Here it is inclosed in a membranous 

 covering, called the chalazae, and receives a coating of thick 

 albumen. The function of the chalazae is to keep the yolk sus- 

 pended in the center of the egg. It does not merely inclose 

 the yolk, but, twisted into cords, extends from either end and is 

 attached to the outer membrane at the end of the egg. 



After leaving the funnel the egg passes into a narrow part of 

 the oviduct, called the isthmus, where it receives the membra- 

 nous coverings which are found just inside the shell. From the 

 isthmus it goes into the lowest part of the oviduct the uterus. 

 Here the shell is formed, and at the same time a thin albumen 

 enters through the pores of the shell and the shell membranes 

 and dilutes the thick albumen first deposited. After this process 

 is completed the egg may be retained in the oviduct for some 

 time. It is, however, usually laid within a few hours. 



Rate and amount of egg production. In the wild state a bird, 

 if not molested after it begins laying, produces a number of 

 eggs varying in different kinds, according to the number of 

 young that can be cared for, and then incubates them. If its 



