CHAPTER II 



THE DEVELOPMENT OF THE CHICK 

 THE EGG 



THE egg of the chick (Fig. 33) is of large 

 size, ovoid in shape and usually some- 

 what larger at one end than at the 

 other. It is protected by a more or less hard 

 shell of organic material impregnated with cal- 

 careous salts. Lying close to the inside of the 

 shell is the shell membrane, which is of two 

 layers ; these two layers, sometimes called the 

 inner and outer shell membranes, are closely 

 attached to each other except at the large end 

 of the egg where they are separated somewhat 

 to form the air space (Fig. 33, a). The shell 

 and the membranes are sufficiently porous to 

 allow gases to pass through them slowly. 



Filling the space inside of the shell mem- 

 branes is the white or albumen of the egg, in 

 the centre of which, in turn, lies the yolk. At 

 opposite poles of the yolk, and apparently 



9 o 



