32 EARLY EMBRYOLOGY OF THE CHICK 



the outer epithelial covering of the body and its derivatives 

 (feathers, claws, skin glands, etc.) , the nervous system, and the 

 sense organs. The entoderm gives rise to the epithehal hning 

 of the digestive tube and of the respiratory organs and the 

 epithelium of their associated glands.^ The mesoderm becomes 

 differentiated to form the fibrous and rigid connective tissues 

 (except neurogha) the muscle, the epithelial lining of the body 

 cavities, the organs of the circulatory system, the blood, the 

 lymphatic organs and the major part of the urino-genital 

 system of the adult. 



