texture of the shell is admirably calculated for 

 preserving the contained parts, and for retaining 

 the heat that is conveyed to them by incubation. 

 Immediately under the shell is the common mem- 

 brane which lines the whole cavity of the egg, 

 except at its broad end, where there is a small 

 space filled with air. Within this membrane, 

 the white, which is said to be of two kinds, is 

 contained ; and near its centre, in an exquisitely 

 fine membrane, is the yolk, which is spherical, 

 while the white is of the same form as the shell. 

 At each extremity of the yolk, corresponding 

 with the two ends of the egg, is the chalaza, a 

 white firm body consisting of three bead-like glo- 

 bules, and it is at these points that the several 

 membranes are connected, by which means, in 

 whatever position the egg may be placed, its va- 

 rious parts are retained in their proper place. 

 Near the middle of the yolk, is a small, flat cir- 

 cular body, named the cicatricula, in which the 

 rudiments of the future chick are contained ; and 

 from these, in consequence of incubation, or of 

 a certain degree of continued heat of any kind, 

 the bird is ultimately hatched. In this process, 

 the germinal membrane, as it is called, or rudi- 

 mental parts of the chick, is observed to become 

 separated into three layers, from the external of 

 which are formed subsequently the osseous and 

 muscular systems, and the brain, spinal cord and 

 nerves ; while, from the middle and internal lay- 

 ers, are formed respectively the heart and blood- 

 vessels, and the intestinal canal and its append- 



