184 



THE DEVELOPMENT OF THE CHICK 



Fig. 106. — The same embryo from beneath, x 10. 



a. i. p., Anterior intestinal portal. A. V., Vitelline artery. 

 Int., Intestinal groove. 



In an embryo of 42 somites (about ninety-six hours), the value of 

 the somites as determined by their relations and subsequent history 

 is as follows: 



1 to 4. Cephalic; entering into the composition of the occipital region 



of the skull. 

 5 to 16. Prebrachial; i.e., entering into the region between the wing 



and the skull. 

 17 to 19. Brachial. 

 20 to 25. Between wing and leg. 

 26 to 32. Leg somites. 

 33 to 35. Region of cloaca. 

 36 to 42. Caudal. 



More somites arc fonned later, the maximum number recorded being 



