THE DEVELOPMENT OF VEBTEBKATA. 



255 



the body wall and mesenteron open along the median 

 ventral line, and spread them out flat, we should get 



SP/NAL COAO 



NOTOCHOAO 



Fig. 133. DIAGRAMMATIC MEDIAN SECTION or EMBRYO CHICK. 

 (Second Stage.) 



. Sf/f/At. COAO 



Fig. 184. DIAGRAMMATIC TRANSVERSE SECTION or EMBRYO Ciuca. 

 (Second Stage.) 



practically the condition in the chick. The difference is 

 again obviously necessary in view of the difference in the 

 amount of yolk. 



