114 THE STRUCTURE OF THE FOWL 



the germinal disc. The remainder of the egg 

 consists of food material which takes no part 

 in the division of the cell, but, by its presence, 

 limits division or cleavage to the germinal disc. 



Fig. 54.— Surface View of the Blastoderm showing the Lines of 



Segmentation, 



A, first line of segmentation ; B, second line of segmentation producing the 

 4-celled stage ; C and D, later stages. 



The first division in the disc (Fig. 54 A) occurs 

 along a vertical plane at right angles to the long 

 axis of the egg, and results in the production 

 of two cells very imperfectly separated from 

 each other. The second cleavage (Fig. 54 B) 



